Well, I went against nearly all the advice provided: Pentax.
For ~$100 under my budget (tack on a couple filters and I've reached my budget):
- Pentax K10D | very lightly used; solid, durable body, rated for > 100,000 actuations (more than I'll ever use)
- Pentax D-BG2 vertical grip / battery holder | really liked the vertical grip on my old Nikon N80, glad I found this at a reasonable price
- Sigma 17-70mm f/2.8-4.5 | decided I wanted the extra reach of the 70mm v. the 18-50 f/2.8; I may regret losing a bit of speed in return for longer reach, in which case I'll switch to the 18-50 with very little, if any, additional cost
- Pentax SMCP-FA 50mm f/1.4 | must-have for indoors, low light, etc.
High ISO performance was a consideration, with the 30D edging out the K10D and N80 in pixel-peeper tests. But unless cropped significantly, I had a tough time telling the difference in high ISO handling between the D80, 30D, and K10D. Given I'm not doing large prints, I'm not terribly concered about it. (The K10D in-body shake reduction also played a role in this consideration, as it provides a ~2 stop edge over the D80 / 30D, given I simply don't foresee shelling out the $$$ for IS/VR lenses.)
As the above parenthetical comment suggests, I ultimately weighted the in-body shake reduction more heavily than the slightly better Canon ISO performance. Even if I decide to splurge on a fast ~70-200 f/2.8 tele zoom (simply can't see myself needing anything longer), which costs about the same - without IS/VR - regardless of mount, the added benefit of in-body shake reduction tipped me towards the K10D. To get IS/VR in a 70-200 Canon or Nikon would cost nearly double, and I just don't see myself spending that kind of cash.
Outside of a 70-200 f/2.8, I just don't see myself going hog-wild with additional lenses, so the far broader lens options for Canon and Nikon don't particularly resonate with me. And as for availability, I've found plenty of used Pentax gear in various places - enough, at least, to satisfy my limited needs and desires.
Other thoughts:
- D80 grip felt best in my hands (perhaps because it's similar to the N80 to which I'm accusomted?), K10D grip next, 30D last.
- Liked the K10D / D80 front & rear dials; didn't like at all the 30D dial on top of and behind the shutter release button
- Liked the K10D thumb-accessible AE-Lock, exposure compensation, and AF buttons; disliked the 30D / N80 top button / finger access to the same buttons
- Preferred the easy access of the N80 / 30D ISO setting hard-button, despite the top / finger button location; no ISO hard-button a downside to the K10D until I learned I may map ISO setting access to the rear thumb-accessible OK button
- Really liked K10D's easy access to DOF preview by rotating the On/Off button with the index finger; felt like a much more natural motion than the DOF preview button on the front/left side of the D80 / 30D
- Liked the K10D swift menu access (Fn hard-button + single directional pad push) to detailed White Balance, ISO Sensitivity, Drive Mode, and Flash Mode settings; didn't play around enough with the D80 / 30D to get a feel for whether the hard-buttons provided same level of detail access to settings (if left to menu access, the D80 / 30D required more scrolling / button pushing to access these detailed settings)
So...there it is. It's clear from the LOADS of really great pictures from all the cameras I considered that the real challenge will be developing my technical and artistic skills (a loooong stretch, mind you, especially the latter). Anyway, just wanted to provide an update. I really appreciate everyone's feedback - thanks!