The rating on my projector is 750 lumens in regular and 600 in eco-mode. I have mine in eco-mode and it has to be pretty dark to watch it.
I'm in a dorm room, so my options for room choice are..... limited... heh. I have to put cardboard up in the windows during the day to block the light out. Watching with the lights on in the room is not an option. With any projector, complete darkness will be best. I wish I could say something like "your room can be at lightness level 4.3 before the image starts to look bad". I'm not really sure how to rate how dark the room can be, but if you're going to be in a basement with small/no windows, that sounds perfect. If I'm too lazy to put the cardboard up, I have to wait until about an hour or so before the sun is completely down before the light levels are good.
As for sound levels, I'm sure my 4805 would be too loud for you. I don't mind how loud mine is because I have 2 computers running with a lot of fans going so I'm used to the background noise (plus I tend to have the volume up pretty high on my sound system.... gotta make the sound as big as the picture hehe). There are plenty of projectors with low sound levels though.
Projector Central is a good resource on a lot of this stuff. One of the nicest features is their screen calculators. You can search for projectors and then when you find one, you can see how far back it should be for a given image size, how far seating should be away ideally, and what gain on your screen would be good for having an image with good brightness for your chosen screen size.
As of right now, I think in the sub $2000 category, most DLP projectors tend to be EDTV while you can get a good LCD based one with HD. For me this wasn't an issue because #1 I'm cheap and didn't get one until I managed to get a 4805 for $999 including a 76" screen, and #2 I don't have plans to have anything broadcast in HD anytime soon. DVDs are basically EDTV so they look great on the projector.
Things are changing pretty quickly in the projector world though. In another year I bet there will be several options for HD DLPs that are of excellent quality right around the $2000 mark. There might even be some now, but as I mentioned earlier, I'm a cheap guy and didn't want to spend more than $1300 so I wasn't considering HD.
AVSforum is a great resource for anything HT. They have tons of threads on Projectors for every price range, HTPCs, Speakers, Receivers.... EVERYTHING!
I found shopping for Audio equipment even more exciting than projectors. I'm glad to hear you're going to get some nice sound to go with your system. It makes me shake my head when I go see someone's setup with a big 65" RPTV and a $99 DVD/HTIB set of crappy speakers.