Their is not that many different types of materials manufacturers can use to produce a soft pillow top. Different types of polyester fiber and a soft foam top may feel very comfortable at first, but will quickly break down and you will be looking for a new mattresses again. The newer memory foam / gel tops / Latex are expensive but they will keep the soft support for a much longer time.
My suggestion is to find the mattresses that is the firmest that you think you can sleep on , because it will never become firmer, only softer.
Also a easy return policy can give some peace of mind.

I didn't like the feel of memory foam, tempurpedic etc but I liked the feel of coiled spring mattresses. I have been offered a "beautyrest haynes way plush pillowtop" for $1500 an adjustable base for $800 and Cambridge Queen Sleigh bed (http://www.jordans.com/Beds/BZ0145410.aspx) for $850. On top of that I will get a 20% discount making the whole combo about $2500. Is this a good deal or should I shop more? Plus free delivery and setup. The store is Mancini's sleepworld but this particular store is not highly rated on Yelp.

But I am concerned about durability and was wondering if the Simmons BeautyRest is as durable as any of the other brands?

Have you considered a Select Comfort (Sleep Number) Bed.
With their adjustable firmess, they should be able to suit almost anyones preference, even as that preference changes. I've slept on one with a 'pillow top' for about 20 years and would be very reluctant to switch to something else. (BTW, No, I'm not connected in any way with the company)

I looked at the Simmons Beauty Rest and iSeries Serta beds and both of them felt comfortable to me. I was wondering as to which would be more durable? Also most mattress dealers don't mention what brand of adjustable bed base would I be getting. Which are some of the better brands of adjustable beds I should be going for?

I would like to go for a Simmons Beauty Rest Haynes Way Plush Pillow top adjustable base + Ergomotion adjustable base. Was wondering as to what is the lowest I can ask a mattress store to quote for that combo.

You need to determine the age of the person that the mattress is meant for. The height of the person who is going to be using the mattress. The best way to purchase a good quality mattress is by visiting good retail outlets and furniture stores like Furniture Zone and Sleep Shop and get a firsthand look at the mattress.