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!
I'm using dual Velodyne MiniVees with my Magnestand MG-12s. Very small(10"x10"x12",sealed enclosure,8" driver,and a 1000 watt amp.Available on ebay for $300-$500
More info here
I struggled with the right low cost sub with my Magnepan MC-1's (down model from your MC-12's). After a few loaners from a good dealer, I settled on the Vandersteen 2wq. I've seen them on A'gon for not too much more than $500. They do require a crossover in your speaker wire signal path that is matched to your amp impedance. I struggled with this also until I found a used Dynamicap. Great match now, plus I hear no degradation with the Dynamicap in the signal path. My dealer who is big into Maggies, tells me he has quite a few happy Maggie customers with the Vandersteen sub. I tend to believe him given my own experience. YMMV.
I appreciate Tasmi's and others reponses to my questions about subwoofers for MG12's.

As I have been reading the responses, I was also cruising the internet to learn more as well as look at manufacturer sites.

I am forming the opinion that a bigger enclosure is better than a small enclosure. It seems that the larger enclosure will allow the speaker to operate more easily without the "back pressure" caused by a small enclosure.

Of course, manufacturers utilize higher power amps to get around the small cabinet size. However, this can only lead to more distortion, which can reduce the musicality of the subwoofer.

So..having frustrated a large part of the audiophile community with that comment, two more questions:

1. if the maggies are supposed to be good to 45Hz, where should the subwoofer crossover be set? I assume that it should be somewhere above the 45HZ in order to integrate preoperly. Any advice on what the frequency response should for the subwoofer?. I am thinking that it needs to be about 20Hz to 150Hz and that I would set it at about 80 Hz.

2. I am drawn to the SVS and Epik products because they are larger and heavier. If i can see my way to roughly the $700 range, I can get into one of these with 12 or 15 inch speakers. Has anyone heard any of the Epik products? Does anyone have any opinions about the SVS boxes versus cylinders?

Your responses are great - please keep them coming!
Depending on the type of cross over you're dealing with, the subwoofer will reproduce frequencies above the cross over setting and the speakers will produce frequencies below the 45 Hz just at lower volume levels. I think it's possible for an electronic crossover, think audyssey type stuff, to completely cut off frequencies, but I'm not sure about that. I think my Martin Logan references setting the crossover at 75% of the rated bottom end of the speakers for a starting point to adjust from.

Focal rates my speakers for 40 Hz to 28 kHz with a low frequency point of 33 Hz. I have a test tone CD that I tested and they were able to reproduce just under 30 Hz, but at a much lower volume. I don't know if your speakers are similar or not.
09-28-10: Bob_reynolds
$500 will not get it done. Besides the sub you need to consider room mode correction to get the most from the sub.
Yes it will, if you know where to shop.

Martin Logan subs (even their inexpensive ones) are designed to match well with their electrostats and other panel speakers. As such, they are very fast, integrate well, and are tuneful, not boomy. They're practically made to order for Maggies.

In fact, the ML subs can make mid-fi satellites sound better than you'd think possible.