Need some good advice

I hate to admit that I am a novice, but I must admit that I probably am in home theatre. I just moved into a home from a one bedroom apartment. At that time all I had was my SONY bookshelf for my movie needs. But now I have a living room measuring 17'-37' and I at least enough that that is just NOT going to get it done!

My car is a different story, I personally really enjoy the sound of Infinity and I have always trusted their reliability and Pioneer as well.
I just purchased a pair of Infinity PRIMUS 250's that will be used for my fronts. Now I just need the receiver, front channel, Woofer, and back speakers. I have a budget of $1800 left (after the infinity 250's) and need to know if I should go 5.1, 6.1, or 7.1. Is a powerful 5.1 more important than a weak 7.1? or vise versa? The purpose of this center will be 95% movie watching. While I mention I personally like Pioneer for the receiver and Infinity for the Speakers, I am flexible. Reliability is a VERY important aspect to me!

Your room is pretty big so if were my money I would move your Infinity's to rear speaker duty. Buy yourself a Yamaha RX-V1400 receiver. Then purchase 2 Paradigm Monitor 9 speakers and the 370 center channel. That should run you close to $1800. You can then set your speakers to large on speaker settings until you can save up some more money for a sub. When you have a sub set all your speakers to small and let the sub handle the bass.
You don't have to get Paradigm, you can get another comparable brand name like Klipsch. I recomend Paradigm cause I familiar with them and the 9's should have enough umph for that size room.

these speakers are an excellent choice http://paradigm.com/Website/SiteRefe...udioSpecs.html i would love to have a souround setup of the studio series!