ProMos chips. Average. Can o/c a bit. But cheap! Don't worry about ram. You can o/c cpu & ram at a ratio that keeps the ram near or at stock. i.e. 8 x 400 = 3.2ghz (cpu) & 400 x 2 = 800mhz (ram) If no go, then 399 or 401.
2) DS3R o/cs better than DS3. It's up to you to decide if the extra mhz is worth the money. 650i is a good overclocker.