You shouldn't have any trouble with your current equipment in there, though you can only put one 5.25" drive in it.
The cooling solution is pretty impressive. A special 200W PSU is included with the box and is not ATX compliant. It seems to be enough to run a 3GHz P4 and a 9700 Pro according to any review I've seen.
I would say overclocking is unlikely to match a normal full ATX system, but it is not out of the question. You'll have to do the manual voltage mod, as there is no BIOS voltage tweak.