Daughter is buying her first home, a 3rd floor condo, it will close in a few weeks, so we don't have access or ability to ask questions of the condo board yet. Part of the flooring is ancient pergo, very worn with peeling edges and some is worn out carpet. The bathrooms, kitchen and foyer have nice black and white marble checkerboard (8" squares) that we'll keep. The condo doscs specify that at least 50% of the floor must be covered with "carpeting, padding, or other sound insulating material". Don't know whether area rugs count yet. We'd lke to get everything teed up so we can install flooring before she moves in.

So, I'm an old school guy-- this is my first condo experience as well as hers. The last time I had to put flooring on a concrete slab I put down a vapor barrier, sleepers, plywood subflooor, and did a nail-down site-finished birdseye maple floor with a walnut/cherry/maple picture frame border around it on top of that (all DIY). I'm getting older and wiser now so am thinking engineered flooring either prefinished or site finished. I might even relent and hire someone to do the work, as I'm supposed to take it easy after a recent surgery.

1. My experience with engineered flooring is minimal. I'm pretty sure, based on reading and walking on a lot of floors that feel spongy and awful that I should be looking at a glue down installation of a plywood core product and put aside my worries about replacing it down the road-- that will be someone else's problem.
2. I'm looking at a product like Isostep Soundproofing underlayment (no commitment to that particular product, just an example) to provide the sound barrier. I assume that on the third floor of a 50 year old building I don't need a bulletproof vapor barrier, just something that wll withstand an occasional spill. Will this feel spongy underfoot if the flooring is plywood core with a thick enough wood layer to withstand a couple refinishings? How does the longevity of foam products compare to cork?
3. Any manufactureres you love for full square corners on the boards and providing long enough boards that it doesn't look like a mistake? DD will pick species and color, I get to vote on the more technical stuff, especially if I end up installing it.