Not to bring up an old thread, but I find myself in a very similar situation as the OP. I currently am an owner of a Sony A100 (my first foray into the DSLR world) and am looking at upgrading. I primarily shoot landscape/cityscape photography, but will be shooting for a website at NCAA football games this fall. Now I know the A100 isn't really suited for this type of shooting with high ISO noise (at higher levels) and a lower fps.
Now I'm not too invested in lenses yet, but in addition to the kit lens have a SAL 50mm F1.4 and SAL 24-105mm lens.
Torn at this point between the 50D and Alpha 700. Really looking for a camera that will allow better sports photography while still being up to the task of landscape photography. Would love the D300, but anywhere I look, its going for close to a $700-$900 more than the 50D/700 (looking at new or old) which puts it slightly out of my budget. I plan on getting the Sigma 70200 F2.8 lens for either model (same cost). Also plan on expanding my lens coverage eventually getting a f2.8 fisheye, as well as a solid f.28 short telephoto lens (in the Sonys case to replace my SAL 24-105).
So basically I'm looking at:
Alpha 700 + SAL 50mm F1.4(since I already own it)
or
Canon 50D