tight sound and tight $ sub for Silverline monitor


I'm looking for a "cheap" musical sub - if that's not a contradiction in terms. It doesn't have to go super low or super loud - just locking for something tight and tunefull to go with some Silverlines in a bedroom. I'm looking for something to add a little impact and flesh out the bottom end a bit.

There are some relativly inexpensive models from Energy and M&K - are there better alternatives? Thanks.
angaria
ML Depth -- very fast, flexible controls, and due to the omnidirectional ("Balanced Force") design, doesn't care where you put it -- even in a corner -- although right between the mains is best.

A used Hsu VTF-2 would be in your price range. Might be a little large, physically, for a bedroom but it's a great sub for the price.