Older is better.
If you're wanting to stay in the 12" range look towards an old Buss, Parks, or Powermatic 100. If you're also looking to increase capacity there is tons of old iron out there - if you're even halfway handy at getting stuff tuned up and going you can find some real steals. Even stuff that is functioning perfectly often goes for less than something new that is garbage in comparison. Names to look for are Powermatic, Oliver, Northfield, Yates, Buss, Whitney, Wadkin, Delta (old, American made Delta).
Don't be scared off by 3-phase equipment as it can be an absolute steal a lot of the time if you're smart enough to wire up VFD or a RPC in the shop.
