You have an amazing setup with 6 of your speakers having the ability to hold their own as mains in any decent sized room (RX8/RX2). With that said the RX8's & 2's will perform best, especially at higher listening levels if you can power them properly. Unfortunately there aren't many, if any, sub $1000 receivers that can come close to 175W power rating that the RX8's are rated for.
The recommended Denon's above are a good route if you're dead set on the $1000 cap and only owning an a/v receiver.
If it were me, which it has been as I also own a MA setup, I would buy a high powered amp and an decent budget a/v receiver WITH Preouts and the features I want. Here is how I would go about doing it:
AMP-Emotiva XPA-3 (200W x 3) $699 shipped. This would power the front 3.
RECEIVER-Pioneer VSX-1121 $399 shipped. This price expires TODAY from newegg.com. After that it goes back to $499. The VSX1121 is the same receiver as the Pioneer Elite VSX-52 minus a few cosmetic differences.
Since they're the same receiver you can use the review of the 52 to see how well it performs:http://www.soundandvisionmag.com/art...eiver?page=0,3