*Most* bikes made in Taiwan and made of chromoly are going to be of fairly good quality. The parts you list sound like a mid-range model (with the exception of the more modern Oryx brake). If you have a bike co-op nearby, you could probably tinker all the changes you're considering. I wouldn't really bother upgrading the wheels unless they're really bad, but an upgrade of tires (and potentially tubes if they're slime) will be a noticeable upgrade.