Jeff:
I will try to answer your questions as much as possible w/o creating a book in the process....answers to all your questions could become quite lengthy.
As far as "which one should I be looking at?"
This seems to imply that you are looking at a pre-prepared kit of some sort. Personally, I'm not anywhere near happy with ANY of the 'kits' available. If you want the best system you can afford, you will want to assemble a system using pieces from several sources.
As for a case to put this in:
Many people here really like the YY cube case (sorry, forget the exact name and model of the thing...just ask around)
Basically tho, the bigger the case, the easier it will be to fit everthing into it w/o having to make compromises in component location. It IS possible to fit an entire watercooled system in a small case, just ask Joe! ie, pro-mini!! but, it's not the preferred method unless you are specifically looking at something that is very portable. Bottom line, bigger is better.
Thirdly, the PSU issue. If you don't plan on running any TECs (peltiers), then the PSU is not an issue. It really only becomes a major concern when you have to power TECs. If you are going to be using a TEC(s), I can't urge you strongly enough to use a separate PSU....don't try and go the HUGE Enermax PSU route...get a separate supply. (flame filters ON!)
Fourth, noise from fans will be entirely dependant on WHICH fans and how many of them you have in your system. You could actually get by with a watercooled system that only uses fans on the radiators and...of course, the PSU. Any additinal fans is purely optional. If you are looking for the quietest setup you can build, like myself, you will prolly want to go with fans made by Panasonic. They have a line called the Panaflos. In this line, they have the model L1a. The L1a comes in all sizes from 60mm up to 120mm...take your pick.
So, if you build a watercooled setup and are looking for a quiet rig, you'll want to either water cool your HOT vid-card, m/b chipset, and whatever else OR use very quiet fans on the HS/F for those components.
Hope this at least gets you heading in the right direction. The deeper you dig, the more detail you'll want. Just ask here, and we'll try to answer. Good luck!