The few heatsinks that they carry (mentioned by Sundog) are grossly overpriced -- $20 for a heatsink that sells for $5 elsewhere. But as previously mentioned, if you "gotta have it now" then they're the best place in the area.
There are a few other local computer shops I've used. Tran Micro (few blocks from General Nanosystems) has a better selection of most things, but their prices are usually even higher than General Nanosystems and their website often doesn't work right. Que Computers is pretty much a "junk store" -- okay for picking up old keyboards and such, but not really useful for much else. And The Box Shop in St. Paul is good for old keyboards, floppy drives, network cards and such. Midwest Computers in Minneapolis is a dump -- perhaps useful if you're looking for a really old Mac, but not worth bothering with otherwise IMO. The few other stores that I've visited in the area aren't really even worth mentioning, even if I could remember their names!
I just noticed that Nanosystems did finally drop the price on the ECS K7S5A to $79. Still quite a bit higher than online, but much better than the $99 they were charging until recently -- and definitely much more in line with what I'd expect a local clone shop to charge.