I am new to this site and to the wonderfully complex world of home audio. I am looking to put together a fairly budget system and could use some help deciding on the set up. I currently have a polk rm6750 system which is just not cutting it. I will be using it for 50/50 HT/music and would like a 5.1 system for the HT use. I am looking at two main set ups. The first is a higher end complete system like the Definitive Technology Procinema 800. The other set up I'm looking at is more of a peice meal set up in which I'd be buying a separate sub, center, bookshelves and rears. I've done research on the bookshelf and subs, but am not really sure how to pair a center or rear to them. Basically, I'd like to know how the def techs compare to a system of budget but well reviewed components I have below. One more note, I live in NYC and am tight on space.

Set up 1 - Def Tech Procinema 800

Set up 2 -
Front Options -
Polk RTi A1
Infinity P162
Usher S-520

Sub Options -
HSU STF-2
SVS PB12-NSD

Center - ???
Surrounds - ???

Thanks in advance for any helpful advice.