Should I go for sub-woofer or new speakers?

I thin u answered your own question...you like what own...and want more bass...wah-la...subwoofer...and for $500...the HSU vt-2 would be the one to checkout...I also hear Aidre has a good one also...at $400...you could spend more...but these are half the price of anything approaching musical sub sound...

Thanks so much for the feedback.

I have to disagree with all of you (I love that :)). Improving your speakers will not only improve the low-end, but also mid and high frequencies, while adding a sub might improve on your low-end, but will also be very unpredictable. The golde rule is: listen to the two set-ups at an good dealer, then arrange a try-out period for your own listeningroom, and then buy with confidence.

Where it my system, I would just buy better mains, too. When you factor in ALL of the cost associated with adding a sub, which is much more then just buying a big black box, you could pick up a really nice set of main speakers that will likely eclipse the current setup w/woofer, likely done for less $$$ to boot.