Integrity by Marvin(Fiberglass), and Kolbe in my opinion but Kolbe will not be that much cheaper(10% at the most)

When I was looking for replacement windows I liked the Marvin ones the best. But they were expensive so I ended up going with the Andersen Woodwright insert windows. Haven't been disappointed after a couple years.

Quite a few companies make the sash kit replacements which it sounds like you need including Marvin. These are relatively inexpensive both in the cost of the windows as well as the labor (can even be a DIY project). I would get prices and I think you will be surprised at how close all of them are. Look at them in the showrooms and you be the judge.
If you look at the Woodwrights that dennisgli mentions above, that replacement window includes a frame and they are a little more money than the kits. Marvin calls theirs the Ultimate Insert Double Hung.

We used Woodland Windows and Doors in Roselle to replace over 40 windows with Marvin casements. I would highly recommend them, fyi.

Eastbay10 - we hadn't considered just doing sash replacement. But can you educate me? I looked up the Ultimate Insert Double Hung on Marvin's website. I am unclear why they would be preferable, but if it can save money, I'd like to know. From what I gather, it would be less expensive, and perhaps maintain the consistent look with the other windows in the house. Is there a reason we should NOT do the sash replacement (instead of the entire window and frame?) Why then doesn't everybody who needs to replace a window just replace the sash and save money? I am eager to understand how this would work. Thanks.

It sounds like you have wood exterior windows, the ultimate insert would have a 4 9/16 jamb thickness which might make it a tough replacement. The tilt packs are the parts and pieces which are must less expensive. I'm not sure how that would work with storm windows, I'm in sunny CA.

Is there a reason we should NOT do the sash replacement (instead of the entire window and frame?)

The assumption when you use either a sash replacement or an insert (not new or a complete tear out)is that the existing frame is in good shape. If there is any dry rot, it is easily repaired. If it is too far gone, a new complete window is your only option.
FYI. The Marvin Clad Insert Double Hung is a 3 1/4" jamb but the wood version is a 4 9/16". I am not a fan of the wood version for that reason.
As to why everyone doesn't go that route, the situation must be right and the client must be aware of it as you are now. Good luck.

Abeg - thanks for your posts, though I was hoping not to have spam responses (and requested that in my OP). Nevertheless I looked at your site. As I mentioned, we are outside of Chicago. There is only one dealer of your MGM windows in a 30-mile radius. I won't buy a window with only one dealer in the region - what happens if that dealer goes away? Also, I'd be sort of "held hostage" by that dealer as there is no one else should I have problems with the windows, and there will be no price competition so I would be paying more than I would for a window with lots of retailers and a healthy competition among them.

I find all these posts very informative, and I thank you all for your advice. Keep 'em coming!

Sash replacements are an option but they can be very prone to air and water leakage if not done by a really good pro.

I did not see what the rationale behind a wood window was anywhere in the post. Is it just your preference in terms of a material choice or do you have some specific interior/exterior requirements?

Try Kolbe's Pocket Replacement Double Hung. I am not sure on the price it may be cheaper and it may not be but it does not hurt to check.

I went with Milgard ultra in my house, based on some of the recs on this board. i definitely do NOT want wood, and they have fiberglass windows, with wood INTERIOR cladding, if you wanted the stained wood look inside. It's really thin cladding, though.
Other option, off the top of my head, is craigslist. Sometimes you can get really lucky. I'm always on craigslist for other listings, but of course, since I needed 30+ windows, it was a different situation vs what you're looking for.

This is my same post to a blog from a few days ago, but answer applies here. Let us know who you go with!
I got new windows installed over the last few months. I wanted fiberglass, brown on both sides. I got quotes on Anderson Fibrex, Milgard Ultra, Marvin and Pella. As stated above, Anderson's Fibrex is NOT fiberglass. When I asked if any vinyl was in the product the sales rep stopped replying to me. I lost faith in Marvin because the sales rep here tried to sell me windows with argon in order to qualify for the tax credit, but failed to tell me their warranty is VOIDED if windows installed at over 5000ft don't have breather/capillary tubes because the seals can pop and glass bows. http://search.yahoo.com/r/_ylt=A0oG78xF119NszsANUdXNyoA;_ylu=X3oDMTBybnZlZnRlBHNlYwNzcgRwb3MDMQRjb2xvA2FjMgR2dGlkAw--/SIG=129s3ps6l/EXP=1298155461/**http%3a//www.marvin.com/download.aspx%3fDocumentID=1547
I ended up going with Milgard. Over the warranty was the best, the product has great ratings, and it was pretty cheap to get triple pane. You can read my blogs here of problems I have had though, but it is not with the product itself. Between the sales rep and the company they have made FOUR mistakes on my order from the wrong size to missing grids to non-matching grid patterns. They were supposed to be done with installation in Nov, and it probably won't all be fixed until March. I still like the product though.

Out of the 4 quotes, Marvin was the most, Anderson was 2nd most expensive.

Whatever you decide to do DO NOT by Lincoln windows. The company who built our home and all others in this sub-division used Lincoln thermopane and everyone has had to replace them, many in the warenty period. However it still costs hundreds of dollars each time for shipping and installation. We have had to replace 10 windows and some neighbors have had to replace them all.

Following up on my OP, we just checked out Weathershield. We will look at Kolbe next. We do not want vinyl replacement or fiberglass. As I said above, the Marvin Ultimate Inserts were priced at $450 each. The Weathershield, which seem to be similar, priced at $385 each. While we are not doing a whole house of windows--we just need two--that price difference is significant to us. But we couldn't see any significant differences in the Weathershield from the Marvin. Please, experts on this forum, am I missing something. Is there any reason not to choose the Weathershield?