Just overclocked with Afterburner and Furmark and a couple observation on the 4650.
Stock core 600 / mem 500 / benchmark 429 / 20 Mh/s
OCed core 700 (max) / mem 550 (max) / benchmark 478 (11% gain) / 25.5 Mh/s (12.75% gain) / max temp 82 deg C
I was able to max out both core and memory meaning this card is severly underpowered coming out of the box.
Memory made more of a difference in the benchmark (about 3 points per 5 Mhz) than core (about 1 point per 5 Mhz) but that is on 3D rendering. Is it a similar impact on guiminer?
I was glad I got to play with the basics of overclocking on this card but it'll be more interesting on a card made for OC where I have to control the voltage (no controlling voltage on this card) and the best performance isn't the max.