Q about image post-processing

This might be better asked in a PSP or Photoshop forum, but I thought I'd try here first as you're a very knowledgeable bunch

I'm currently scanning in several hundred slides (originally taken with Pentax ME Super & K1000). Some are quite old. The Canon 2710 slide scanner I'm using does a pretty good job but there is invariably a lot of noise on each scanned image, especially in the darker areas. Most of the slides also need adjustment in terms of the white balance/colour, which I'm doing using PaintShop Pro XI. PSP also has a Digital Camera Noise Removal facility, but I'm not sure whether I should fix the levels first, then remove the noise, or the other way round : I've tried it both ways round but still can't decide. Scientifically, which way should work the best?

/WiRED