A couple of thoughts. As noted, the Thiels are not a current model. If you are going to do a center and surrounds, it might be something that is a bit harder to do vs. a speaker that is a current model and the manufacturer makes current center and surround speakers. The size should not be an issue. It is a bit smaller than my bedroom (probably 13.5x17.5 but has a tray ceiling so it is a bit more volume). I have a BDP-93 in the bedroom. It's good for an all round piece and a great Blu-Ray and DVD Player but it is not something I'd call audiophile playing CDs. It's not an issue for me as my bedroom system backs to the main system and the balanced outs of my Bryston BDA-1 DAC go to the main system preamp and the RCAs go to the bedroom. So I can play any of the sources hooked in the main system, including the Squeezebox Touch or the HDMI Audio De-Embedder I have hooked to my modded BDP-83 to extract hi-rez PCM from SACDs.
Decide on a budget. Don't ignore sources like accessories4less.com where you can get a factory authorized refurb from Marantz (or Onkyo). I got my basement receiver and an exteneded warranty through an independent co. (Warrentech) that way. A Marantz pre/pro will be good for music and movies. I have a Marantz SR6003 (receiver) in the bedroom (and it makes an excellent preamp and I have a Bryston 3BST for the left and right channels). Decide if you need something like 3D. If not, you can snag a bit older model sometimes at a really good deal. Cary would be a good choice as well. I ended up with a preamp (with HT Bypass) and a separate processor in the main system as new digital technology changes fairly rapidly and then you have something that is obsolete to an extent. People who are into HT without being an audiophile, which is probably most people, usually don't want yesterday's technology except at a steep discount. I snagged an Integra pre/pro for the main system at a great deal on Craigslist (the guy just wanted HDMI 1.4 for 3D) and I could sell it for 35-40% more than I got it for ($600) and it sounds great on movies.
If you are going to do surround (or even if not), layout your room with regards to seating and where components and a TV would be. That may dictate certain constraints. Don't overlook the used market (Audiogon, Craigslist amoung others). Once the room is laid out, go take your favorite CDs and listen to speakers. By then you should know what will fit, whether you want floorstanders or whatever and once you do that you will be ready to make purchases of the various components.