Subwoofers

My room is approximately 20 ft x 35 ft.  I'm using two REL S/510 in a stereo pair.  Using speaker level connections for two channel.  I have the gain and crossover set really low. They blend well with my full range speakers. 

If I turn them up very high, it's too much.  I can't feature needing bigger subs for two channel, but I haven't heard them. 

They don't have enough oomph for home theatre. I have a larger SVS sub that kicks in when I'm watching movies 

@greywolf I haven't heard the Revel, but I notice that it only has line level inputs.  Maybe that works for you, but I like connecting the REL with speaker level for two channel.  It also has separate line level inputs for a LFE channel if your system doubles as a home theatre line mine does.  You can use both inputs simultaneously and it has separate gain controls for each.  

I also noticed that the crossover frequency is shown as 50 to 150.  To get my subs to blend, I'm considerably lower than 50. Not sure if that's a problem.

The really nice thing about having high level and the LFE input is that I can set the high level output low for music and crank up the LFE gain for movies.  If you are using the subs for home theatre, I think I'd go with the REL S812 if you like loud explosions, etc.  The S510 would work for some people, but I like a little more for home theater especially in my large room.  I don't know if other subwoofer brands will also do this. Perhaps they will.

I lucked out and got both of my REL subs new for under $4500.  You probably won't get a deal like that, but I would guess that some of the larger online resellers would discount 10% if you call them (Music Direct, Audio Advisor, Crutchfield, etc).