I Need Help Picking a Sub

Hello all. Right now i have put together of a somewhat decent theater system in my small living room. I need help with a sub woofer because i dont know what to buy. I am giving myself a cap of $1400 for something used on audiogon. I have Martin Logan ascent front and center speakers. I have a sunfire pre and 5 channel amp all of which are balanced connections. i am looking at the revelB15 sub or perhaps a velodyne DD series. because my space is tiny i was thinking nothing more than a 8" woofer but someone told me to stick with nothing lower than 10" for clarity. i could use some help from those audio pros out there.
I think you would do well with a REL Strata III sub. They are going for a song now and should fit well with the Logans.
I like the REL subs as well but you need to be carful with differential amps and how they work with the high level (amp output) connections. In most cases you will get a hum through the sub will some varying degree of loudness. It drove me nuts and I eventually went with a sub that worked best with line level inputs (Focal Electra 1000)
I would think one of Martin Logan's own subs would be a perfect match.
I think your Velodyne DD choice is a very good one, but I'd try to squeeze a 12" driver into your room instead of 10" -- I wouldn't even consider 8". The great thing about the DD series is the digital EQ. And they accept balanced connections.

A much less expensive alternative, without the digital EQ though (does have an analog PEQ), is the SVS SB12-Plus -- 12" driver in a small sealed box with XLR connections.
IMO REL subs were OK before subs started offering EQ programs. I never cared for REL's down firing driver which I believe they've finally given up on.

With your budget you should take a long look at either Velodyne DD series or JL. The JL seems to have a better build quality but the Velodyne has a great setup program. The last JL review I read the reviewer used the Velodyne to graph their differences and to adjust the JL into his room.

The Velodyne is an older design than the JL but there seems to be a lot more JL's on the used market.
Martin Logan makes great subs. I use two Martin Logan Dynamos and they are very good small footprint subs.
I agree with Rcrerar and Cruz123; I currently own the ML Grotto and have owned the ML Depth; they both pack the punch for HT and are fast enough to keep up with your Ascents. You state your room is small and your budget $1400; my two cents would be to go with a Grotto which you should be able to get on A'gon for around $600; if it is not enough for your room, get another one. As another option, I currently have a Grotto and a HSU VTF-3 HO in my HT; I run both during movies for the explosions etc., but when I listen to my concert DVDs, I turn the HO down somewhat and let the faster Grotto do the majority of the music. You should be able to find an HO for around $650 on A'gon. This gives you flexibility- good luck in you search!
To tame your small room with pinpoint accuracy of low frequency tones the best sub choice you already made is the DD go for a used DD 10 or you can go for the cheaper velodyne spl 1000R. both have excellent equalization option.

The JL Audio may produce a little more bass at high volume which you seldom may use but the sound equalization settings are not so great.
The james EMB 1000, 1200, 1500 are very depending on room size, the ML ones mentioned are also great, and the JL Audio, and Rels.
If I had ML speakers, I'd sure look at ML subs first.

But I really do like my DD15... but sometimes wish I had gotten the DD18 instead.

Subs aren't about loudness so much as they are about depth.... and you can use the volume knob on them, ya know. Get a DD12.
Depending on your budget, check out the Vandersteen or Outlaw Audio units.
SVS would be my first choice. Money back policy can't be beat.
Velodyne DD10

Thanks guys for all your help. I will be deciding in a few weeks to purchase my new sub
Matching ML may be best. I'm very happy with a SVS Ultra 13 for both HT and music. It was $1,500 direct from SVS as refurbished with their full warranty. Very user friendly with several connection options and sound set-up adjustments.