Subwoofers

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).

Why REL?  You'll get a lot more bang for your buck, and great sound with a pair of Rythmik G25HPs.  With REL you're paying at least half the price of the sub for marketing and dealer markup.  With Rythmik (and other internet direct options), there's not all that overhead. 

If you're worried about the durability of the Rythmiks, I have had my F25s for about 8 years now, and am not the original owner.  They are probably at least 10 years old.  Amps and replacement drivers are still available in the event something were to fail.  

If foam surrounds on Rhythmik subs are an issue for you, why were they even on your list in the first place?  Also, I’ve never, ever heard of anyone having an issue with a Rhythmik sub.  Crossing Rhythmiks off your list simply due to foam surrounds would be a mistake I think given the performance, value, and overall quality on offer, but that’s me.

I have heard and owned a lot of subs and the JL Audio Fathom series are super deep and powerful.  

Honorable mention to the SVS SB3000 which are app adjustable, have excellent impact and a very likeable tone.  

I didn't see that model had foam surrounds, excuse me. 

Maybe it's me but I find Rhythmiks site hard to navigate.