I have an onkyo 304 receiver and some sony floorstandings and center. I bought the sony subwoofer and I must say its not much of a difference from what the fronts can do with bass. I need something to add more life to the film. Just not on gun shootouts but more for general atmosphere. Trying to stay under 300. I know its modest but not too bad for a college kid.
Cheers

If you can manage to pull together $325, I think the eD A2-250 is a great choice. Here's a link to the product.

http://www.edesignaudio.com/product_info.php?cPath=2_41&products_id=406

Being a poor college kid myself, I totally understand your need for a budget sub (heck, I'd love pricey B&W/Paradigm speakers but it ain't gonna happen right now). Do be advised that you're probably in for a 1-2 month wait if you choose this sub, but it should be a VERY big step up from your Sony. I think it'd be worth it :). Good luck.

Ive heard about this sub and I would love to own it. Thanks for the idea but im pretty impatient to wait two months! haha . anyway would this jbl sub be any better or is it pretty much just apples and oranges. http://www.bestbuy.com/site/olspage.jsp?skuId=7706477&type=product&id=1138085815961

This (http://cgi.*********/BIC-Acoustech-H-100-12-500-Watt-Powered-Subwoofer-NEW_W0QQitemZ140220166830QQcmdZViewItem) is the popular recommendation on this forum, probably better than JBL and you might get lucky with $200 offer. No wait either.

Out of curiosity what model Sony sub do you have?

sa-w3000

Yeah, if $300 shipped is a hard limit, then I'd definitely recommend the Bic Acoustech H-100. I have one and love it. The AV123 X-sub is about its only competition price/performance wise, and the Bic is considered slightly better for film (music is the X-sub's ace.) Wait times might be long for it, though.

However, at above $300, the eD sub mentioned starts to leave the Bic in the dust. Something to consider.

At certain pricepoints, different makes subs are considered the best buy, and if you can add some more funds, other subs suddenly step into the light. :)

sa-w3000

Have you tried the sub in the corner. Give it a try and turn it to 12 o'clock. You should be able to tell quite a difference with the sub in the system.