Best / Cheapest Rear speakers for 7.1

The Speaker Company...Excellent price and users have been highly speaking about them.

That is fine. Any receiver can drive a 6 ohm load no problem. When you get to true 4 ohm speakers you may have to worry about your AVR being enough. Just level match (or run Audyssey or some equal).

I wouldn't worry about Paradigm unless you listen to a bunch of 7.1 music. Any decent speaker will be just fine.

You could build these from a kit if you want the most SQ for that budget, read these impressions on them.

I was in your situation as well with 100's, CC690 and 20's. I listened to a pair of v6 atoms and bought those. Havent done any critical listening but as much as I use 7.1, I believe they'll do just fine.

The Emotiva ERD-1 surrounds are 4 ohm, but surround speakers aren't going to stress a receiver all that much. The price is right. Take a look.

I have a pair of them and find them to be very good, especially for what they cost. They come with wall mounting brackets and only stick out 5". They are also dipole design.

Direct radiating speakers are usually recommend for the rears in a 7.1, although some people do use dipoles or bipoles.

The cheapest solution would be to use some old speakers you or a friend have lying around. Otherwise, any respectable speaker will do, and you've already received several fine suggestions. It may not be an audiophile's nirvana, but in reality you have quite a bit of latitude with the rears, especially if you have an AVR that EQs them. For a couple of years, I used a pair of Cambridge Soundworks Newtons I bought for a song at their outlet store, and they blended in just fine.

The Emo ERD-1 has switches so you can go from dipole to bipole. Kind of a two in one.

I find they have a very good dispersion to the sound. I'm using them in 5.1.