I don't think 23 lbs is too terribly heavy for a geared bike, maybe a little bloated for a SS, but in reasonable range. Yes, 650-750 is a good deal. You know the frame price new, and to get a complete bike for that price isn't bad. I have a rockhound and a ruffian, and they're great mountain bikes.
My rockhound, though it's a 29er, is a tad about 25 lbs, size 17". The ruffian SS, fully rigid, is at 22 lbs, again, 17" though 26" wheels.
If you're super concerned with weight, then a steel bike probably isn't your best bet, a 13" frame probably weights a shade under 4 lbs, where those fancy carbon frames are at under 3. But if you want a great all around bike then the gunnar is terrific! Good luck!