I don't think there are too many IS solutions in the lowlight lens category.
There's a Canon 17-55/2.8 EF-S IS that would probably make a good alternative to your kit lens and would work well in low light, however, its almost $1k
http://www.digitalfotoclub.com/sc/product-features.asp?id=964602994http://www.photozone.de/8Reviews/lenses/canon_1755_28/index.htmAnother good concert lowlight lens is the Canon 70-200/2.8 L IS however, this one also breaks your budget and I don't know what kind of range you're looking for, this one might be to much zoom for you.
http://www.digitalfotoclub.com/sc/product-features.asp?id=964585410http://www.photozone.de/8Reviews/lenses/canon_70200_28is/index.htmIS is kind of hard to come by in a good concert shooting lens from what I've found. However, I haven't really found where I need it, if I shoot at ISO800 or ISO1600 and wide open.
I'm currently using the Tamron 28-75/2.8 for most of my concert/club photography. Its a very sharp lens and does well in lowlight settings. Its also in your price range.
http://www.digitalfotoclub.com/sc/product-features.asp?id=964588098http://www.fredmiranda.com/reviews/showproduct.php?product=187&sort=7&thecat=29If you wanted to step it up to the next level you could go with the Canon 24-70mm/2.8 L - however, this one is close to $1k as well.
Also, if you don't have the fantastic plastic, Canon 50/1.8, you might want to grab that. It works extremely well in low light situations, is very sharp, and only costs around $80.
http://www.digitalfotoclub.com/sc/product-features.asp?id=226523065http://www.photozone.de/8Reviews/lenses/canon_50_18/index.htmAnother good lowlight prime is the Canon 85/1.8. Its also very sharp and isn't too expensive.
http://www.digitalfotoclub.com/sc/product-features.asp?id=226523068http://www.photozone.de/8Reviews/lenses/canon_85_18/index.htmMy suggestion would be to go with the Tamron, although its not an IS, I've found that if you set your camera to burst mode, and jsut take few pictures at a time, you're bound to get at least one or two that aren't shakey or blurred. Plus, I've heard a lot of photographers rank it highly and even say it competes with the Canon L lens in that range. Then I'd grab a prime, like the 50mm or the 85mm which will work in extremely low light conditions and still produce clean, sharp images.
Another thing you should consider when buying a lens is your plans on updating your camera. EF-S lenses are made for cameras with the 1.6x crop. If you ever plan on moving up to a 5D or a more professional camera, you'll want full fram lenses as opposed to EF-S lenses.