Two JL F212s verses two Velodyne 18 plus?

Clean output capability and damping control would be my top priority, were I in your shoes.

I suspect that either of your options will be great in your modestly large room (on that basis), so you probably can't go wrong, but...

If you don't have Audyssey or equivalent, then I'd add stand-alone Room EQ (at least for the subs), if you choose the JL. SVS sells a bass-only version for the sub signal - under $1K and, judging from my experience with the similar Velo SMS-1, a critical component of good sub performance.

The Velo DD series includes an excellent version of this approach, and I'd choose it over the JL (which includes a more rudimentary version) on that basis, but....if you already have the capability in your Pre-Pro/AVR, I'd probably go JL.

You might want to look at some other options, as well. A pair of the big Rythmik dual driver subs (F25) will be far less expensive and (based on my experience with their smaller subs) probably still provide top notch perforance. SVS also makes a highly regarded product that's a lot less expensive than the big JL or Velos.

Good Luck

Marty

GHaas,

Since you're using a pre-pro with ARC, you might want to consider a pair of the Rythmik F25s that I mentioned earlier, and linked here:

http://www.rythmikaudio.com/F25.html

A pair of these will provide MASSIVE clean output capability for a room your size and even at <$3K for the pair, they might well be everything you want. If they are not, the F25s are sold on a money-back, in-home trial basis.

Good Luck,

Marty