i'd prefer to make a $1700 purchase of a used radio from a REAL ham radio store for warranty reasons. even 30 days is a good thing. turn it on & LEAVE IT ON, key as often as you can, on different bands, even if only to yell CQ or have a brief qso before work, bedtime, etc. 2nd best would be a local who'd let you play with it before you bought it. as much as i've bought & sold on e bay, i'd be hesitant to part with $1700 there....
that said....i'd certainly consider a used pro3. less troubles then with the 746pro, which did cost around 2 grand at its peak, for definitely 1 step down from the pro3. so now you're looking at a 'better' radio for less cost, albeit used. why better? without going into technological mumbo-jumbo, more bells & whistles truly translates into a better receiver and a little more in the way of available tweaking. transmit, same. i think the only drawback to the 756 series was a lack of 2 meters.
unfortunately, icom left those yearning for a mid-ranged in price radio in the dark by discontinuing BOTH the 746pro & 756pro3. they go from the 718 @ $600 to the ic7200 @ $1100 to the ic7600 @ $4000 to the ic7700 @ $7000 to the ic7800 @ $13000. i feel as though the 7200 is like yaesu's ft450.....it's there, but what niche does it really fill?
i doubt the 756pro3-used-will drop much from the current price range it is in. look for a MINT one & jump on it!