I'm looking to upgrade my Canon T1i after 2 years. I'm not sure which one I should upgrade to though. I'm not thinking about going full frame either, it doesn't really suit me. (My main focus is portraits, landscapes, group events, and occasional basketball games)
* "amazing low light performance" on the 7d :-)))
Whoever told you that? The 7d has got the same sensor as the 550d/600d/60d, and it's main drawback is that above iso 800, noise reduction will blur you picture at crop sizes noticeably. And af is determined by the lens' light capability, too, so for fast phase detect af in low light you should have a 2.8 or better open aperture.
* weather sealing: The 60d is weather resistant, too, much more than the cheaper rebels. But that won't do you any good: your *system* isn't sealed if you use non-sealed lenses, and all of yours aren't! And you could think back of how often you were tempted to shoot in the rain anyway.
* I try to be not in the habit of recommending my own gear (60d), but I cannot resist: It's drawbacks over the 7d are less weather sealing (see above) and much worse af (do you track moving objects often? for "occasional basketball games" it'll do, too) and 8fps instead of 6fps (if you're not into pro event photography, do you think that'll make a difference)? And the 7D doesn't run magic lantern, which is a must for video and has great value for still shots, too.
* My recommendation: 1. get better lenses. 2. get more better lenses. 3. get the 60d if you must upgrade now and need more megapixels to be able to crop more... did I say better lenses do make the difference? Now I wouldn't recommend anyone to go over the top and buy a 24-70ii for a 1000d, but your current lenses are crappy, the 15-85 is worlds better, not to speak of a good macro (like the 100L as a combined portrait lens), fast quality primes or L tele lenses.