In short: yes, a powered sub -- if it's the right one -- could definitely enhance the performance of your system. There have been a lot of posts on this subject over the past 3-4 months. I contributed a long piece which summarized the results of Widescreen Review magazine's tests of some 50 subs -- you can look for the post in the Audiogon archives, using the phrases "Widescreen Review" and "subwoofers".
Also, look for posts from other regulars on this forum. My personal experience with powered subs relates mainly to my Vandersteen 2Wq subs, which I think are outstanding, but other members of the forum have made excellent posts about other brands/models that will be informative for you.
Also, look for posts from other regulars on this forum. My personal experience with powered subs relates mainly to my Vandersteen 2Wq subs, which I think are outstanding, but other members of the forum have made excellent posts about other brands/models that will be informative for you.