How much do you have to spend, to get a good Sub?

SVS 12 " sealed subs start around $650. They have a great rep and are outstanding performers on the test bench. The 12" Rythmiks are about $100 more (last I looked), also test very well, and perform beautifully in my own system.

The caveat with subs (for me) is always integration. The odds of successful integration are IME much, much higher when you use digital bass management software like Audyssey (or the equivalent).

That raises two issues:

Are you comfortable with that approach?
Have you budgeted for that approach?

You can replace your preamp with an Audyssey XT 32 (their top version software) enabled pre-pro from one of the mainstream Japanese hifi companies for app. $1500....if you're willing to go that route. If you're not enthusiastic about that idea, HK makes a similarly equipped integrated amp for similar money.

If you prefer the traditional 'Phile's purist high end approach, I'd think twice about adding a subwoofer. Many here will disagree, so, as always, remember

YMMV
IMHO
etc

Marty

If you are buying new, a good subwoofer that will be relatively easy to integrate into your system (which requires, as others have noted, that the subwoofer have some sort of automatic room correction software) will run between $2400 and $3200, minimum -- cost goes up from there for bigger drivers and a little deeper response. Good brands to look at include JL Audio, Velodyne, and REL. I would caution against buying an off-brand without auditioning it first -- a lot of them are just glorified boom boxes.

What's your budget? For music I'd go with a pair of sealed subs. You can get a pair of SVS SB12s for $1149 and free shipping. Tough to beat I'd think. I echo Marty's point about incorporating some form of integration software. Best of luck.

I am thinking of a M&K X10 sub ( M&K inventors of the Sub) any thoughts?