Two subs or not Two subs?

Used RELs (ar any good sub) can be the way to go...I have a room about the size of the one described, and my single REL Q150E (circa 2001 10" forward firing) sounds great set around a third of its volume knob setting...adjusted slightly up or down here and there depending on the recording (I put a "chicken head" knob on the gain pot so I can easily tell what's what without turning the sub around). 2 RELs like this seem like overkill, but I'd buy another Q150E if I found a used one cheap enough just because I like it so much. Interesting article I read recently in a UK hifi mag about a REL sub...the writer was listening to some mandolin music and took the sub in and out of the system...you wouldn't think mandolins would have any low frequency information, but the music sounded much better with the sub on...go figure...I've done similar experiments and am amazed at how low the output on a sub can be and still add MOJO to whatever I'm listening to.

I would buy one good sub over two OK subs any day of the week.

Are Rel's the best option for high level connections right off of the amp or are their other brands with the same type of connection that work better. Price range $0-$800

I used a single REL for quite some time but always found it directional, no matter where I placed it in the room. Meaning, that I could always detect just where the bass source was located.
I now have a pair of ML Descenti's and the integration with the main 2 channel speakers is great and they are so much more 'tuneable' than REL's. Descenti are not cheap but highly recommended.

You can go to AVS forums in the subwoofer section and look for the ancient subwoofer shootout thread.
Look for the best used sub that $800 can buy. SVS sometimes has scratch and dents for a good price.
For this kind of money you should be able to get amplified Hz just below 20.
Just be warned; I set a $ limit then eventually doubled it.
A quality powered sub will last a lifetime.
No regrets.