If the fence on your C'man is the twist handle type with a little tab at the back, its a good thing you're getting rid of it. Having used one a long time ago I can tell you its basically a POJ with an extremely unsafe fence. Its certainly not worth putting a $300 fence on it.
The Unisaw is by far the best of the lot, but the 3 phase motor is a deal breaker for that price. 3 phase machines are generally much harder to move, so he has no leverage. Common sense says a shop with 3 phase power is likely commercial and they aren't likely to take a chance on an old, rebuilt machine.
If you replace the motor with a single phase 3HP ($300+ & you'll have to replace the switch, too $100), offer him $300 with the explanation. When he says no, just watch the ad & when he's been sitting on it 30 days, call him and repeat your offer. By then he'll be more motivated to move it :-)
But seriously, if you're not experienced with aligning tables saw, etc. you're better off going with a new machine, considering things like its new, has a riving knife, warranty. IMO the Grizzly hybrid 2HP unit looks like a good entry level machine that will do the job for 90% of hobby shops. Its certainly far better than the average contractor saw like Rigid or Delta.
Good luck, but don't stop looking for the old iron.