Earlier these deals were showing as expiring at midnight PST tonight. The countdown timer is no longer there, so they may be around longer, but if you are ready to buy, just do it!
A pair of these for $162 each (or $324/pr)
Infinity REFERENCE 253 three way floorstanding speaker has powerful sound, deep bass response and elegant design that accommodates any home theater system.
www.harmanaudio.com
one of these for $162
Infinity REFERENCE RC263 dual three way center channel speaker accommodates with any home theater system & has crystal clear sound quality with low distortion.
www.harmanaudio.com
That gets you the front three for $486! I know that is way under your budget, but these are great speakers and the center is the best center I have ever heard - I assume that since you are talking 5.1 that your emphasis is on HT so the center is important to you!
That leaves you with $1500 to $2500 for your subs (we would recommend two) and AVR.
For the AVR, get this:
So that leaves you with $950 to $1950 for a pair of subs. Like I said, I assume you are about HT and or gaming. If you were 100% music, you could save money with subs that do not get all of the way down to the low (or below) 20Hz territory, but for HT, unless you are in an apartment where you need to be sensitive to your neighbors, you will want to spend at least ~$1400 for subs. I don't know of any killer deals right now on good HT subwoofers, and we need to know more particulars like your room size and how much of your listening is music%/HT%/Gaming% to make good subwoofer recommendations.
Again, the low cost of these speakers may scare you, but trust me, they are great speakers being clearanced at a deep discount and a couple of good subwoofers will easily take half of your budget!
Edit: I should ask what type of music you listen to because some genres of music do involve the kind of high output at low frequencies that I would normally consider only needed for HT!