Yep those will be fine together. I suggest the 1GB version as it is a bit faster due to the momory bus. I would overclock the x4 635 a bit for games.
i will OC athlon to about 3.2ghz with stock cooler and later maybe i will buy new cooler and OC to 3.6ghz. i think athlon is better than phonem because their price, x4 635 cost 140$ and phonem about 230$.
ram will be ddr3 2gb first then 4gb later.
i will buy 2gb more ram after few months.
i will play all new games i missed: gta 4, mafia 2,assassins creed 2,crysis,GRID ...