REL S510 or S812

I also recently purchased a REL S510 for my 2-channel system to supplement my PMC Fact 12 3-way floorstander speakers in my den which is 12' x 17' x 10'h. Does exac tly what oddiofyl says; except I have it crossed over at 40 Hz. Fills in wonderfully and creates broader soundstage. I also debated about going larger with the S812 but glad I didn't since the S510 was more than enough for my room and setup. You'll love it- looks great as an added bonus.

Paul at PS Audio is a big fan of Rel.

I've had a pair of REL S510 for two years that I use for both my HT set up and my 2-channel system. I'm a huge fan of REL -- I like that you're able to have HT and 2-channel connected at the same time each with their own adjustment. With my systems, the sound is spectacular. Like you, I debated between the S510 and and S812 and while I have no doubt the latter is even better than the 510, I determined that the smaller one was more than sufficient for my room size and system -- and that was a good value decision. The only other thing I'd say -- they're an incredible addition to a 2-channel system and if you can swing it, buy two of them. It really adds to the soundstage depth and breadth. Good luck.    

I own 2 rel 510s. Unless you have a very large room, the 510 is plenty. The volume is at about 25%. They add depth to the soundstage and the low mids are great. I use them in my ht as well. The biggest issue is that some music producers use too much bass and some low notes resonate in the room.

I own 3 older RELs (Q series) bought used for  around 200 bucks each...one is in my video system. They all work perfectly, and although they're not under warranty (and REL won't repair them) they're so inexpensive that they've more than paid their way over close to a decade.