yes and no, the 6200 shouldn't be underestimated, they can overclock to run faster than the 6600 (not GT) just make sure you get the non TC model. non TC is really a 6600 core with 4 pipes disabled. TC has its own 6200 core, with only 4 pipes, so none to unlock.
also, dont buy a chaintech motherboard, in my experience and from what i have heard, most chaintech stuff is fairly crappy, go for an MSI, DFI or dare i say it -Asus- motherboard.
that PSU is fine. to say "over 420W regardless of system" is just stupid.