i had the hp dv3z till it die on me recently (cpu kaput based on the LED error code). Dota 2 is playable on turion x2 + hd3200 provided you turn down ALL settings and put your render quality to low. It looks horrible imo much worse than regular dota...

side note, the hd7670m can max this game out at 1366 x768 no problems.
max temps is 80 without cooler. not bad... not great either.

From notebookcheck the 7670m is slighly faster but realistically they are pretty close.
I am using the 7670m and the lowest fps in dota 2 is around 30 when team battle but it usually averages around 60 ( all settings on high).
If you have games that utilizes Physx or ur an nvidia fan then get the gt630m..