Don't be too scared of the used market - its very uncommon for someone to not take good care of their rifle. Ask for pics, and a round count. You'll save yourself a few hundred bucks - however, if your OCD (I'm just as bad) bugs you more than the few hundred, then buy new.
The Vortex PST or HS-LR are nice choices. I read good things about the sightron as well.
If you're going to reload, buy ammo with good brass that you can keep and use later on. Nosler or Lapua, I'd suggest.
I have long arms too, and I've had to add a pachmyr recoil pad to add length. My T3's didn't fit right out of the box. If you're going to add a boyd's stock, you can have a custom LOP made for you.
You won't regret a T3. I'll buy you a beer if you honestly feel different in a year....!!!!
-J.