Inexpensive sub for MG12's


I have been listening to my new MG12's with a 15 year old Acoustic Research sub that is a 12 inch with 175RMS amp.

The sub sounds a liitle bit boomy, there is no deinition or timbre to the bass, it cannot be adjusted to a 45 hz cutoff, and I suspect that sub is a little bit slow.

What alternatives are out there for about $500? That is my current budget given the WAF is very low over the Maggies (size along with sittng on 14 inch high wood cubes about four feet from the walls). The new Denon 103R and a SUT did not help either I suppose!

I want to make a large step up sonically and if $500 cannot do it, I want to know that so I can decide to wait until stereo spending would be more acceptable to my better half.

Advice is appreciated!
dsper
10-06-10: Bob_reynolds
Johnnyb53, with all due respect, the OP stated he wanted to "make a large step up sonically." A 10" driver in a relatively small 30 pound box is not going to make clean bass at anything much above a whisper in a small room. Any sub can be boomy with the right (wrong) setup. The ML sub you referenced is ported and as such we can expect its group delay to be higher and therefore, sound "slower," than a sealed design.
Right you are. I meant to recommend a sealed ML, and when I saw a $500 ML sub I got too excited. I really meant something more like ML's Dynamo 700, which is 300 watts and a sealed enclosure. While it's a little over budget, it's within reach at $700. It's also roughly a one-foot cube, which should help the WAF consideration.

I was figuring that the volume needs would be modest since the MG12 is one of Magneplanar's smaller models.
I have the Dynamo 700 and rarely use it above 1/4 volume in home theater mode. When I had it connected to the main channel pre-outs the volume was even lower. I was amazed at it capability when it first arrived. It's not the greatest sub on earth, but considering it's size and price I'm impressed.
ML subs are very hard to beat. I use the Dynamo with Martin Logan stats. Perfect blend.
I've had Maggie's in the past, MG12's, 1.6's and MMG's. A sub that I found integrated with them very well was an Onix Rocket UFW 10. Super fast and very musical. Not your typical "home theater" sound. Keep your eyes open and you can usually pick them up used pretty cheap; hey, with the budget you have, you might even be able to get two and run them as a stereo pair, one on each side so each MG12 would have its own pet subwoofer; now that would be cool! ;)