The second floor of my house is the original hardwood from 1964 which I'm guessing is Oak (or Red Oak, how do I tell exactly?) with a typical/generic golden finish (not quite natural or gunstock but the typical in between finish). It is a 2 1/4" wide plank...The first floor entryway currently has slab tiles leading into ugly blue carpet. I'd like to rip up both floors and put down hardwood in the entire area. It's just over 400 sq. ft. at 32'x13' (gets narrower in sections, etc)

After some research, it seems like engineered hardwood would be my best bet. I'd like to go right over the slab to keep the height down. Any and all help & recommendations to a newbie would be appreciated...

Should I lean towards lock & fold or T&G w/ glue? Or go glue down all together?
I don't mind dealing with glue too much as I did tile the kitchen myself. Which application would I get the most bang for the buck?
I'm trying to stick with a $4 or up to $5 sq. ft. budget
Are there any brands that I should try to stick with?
What do you think about some of the lines that Lowes carries such as Bruce, Natural Floors by USFloors, etc? I did take a look at Bruce # E2106 which is a 3" wide Butterscotch Oak lock & fold plank that was recommended by Bruce after speaking w/ their tech line. Lowes had it in stock but after looking at it, it looked to be many ply's with a VERY thin veneer. Is this what I'll be dealing with in my price range?

What about Lumber Liquidator's Schon, Mayflower, Virginia Mill Works?

What type of prep. and underlayment should I go with over the concrete slab?

I'm definitely a 'do it once and do it right' type of guy and I'll be in this house for the foreseeable future, so I don't want to skimp but would like to keep my budget in check.