[KarmaKiller]

The Mobo in the pic is the one I linked to in the post. (I forgot it the first time, then edited)

If it were me though, I'd go ahead and put in the good PSU now, saves some headache for later.(Of course if you can afford it now)

And for a cooler, what's you budget? The best air cooler you can get will run ~$80. A moderately good one will run about $50.
The Zalman is a good cooler at best IMO. These are much better. (In order of price)

Thermalright IFX-14 Internal Fire eXtinguisher AMD & Intel CPU Cooler (Socket AM2 / 775) - FrozenCPU.com
$80+ Fans

Scythe 5th Anniversary "Ninja Copper" Six Heat Pipe CPU Cooler - LGA775 / 478 / AM2 Ready (SCNJ-1100P) - FrozenCPU.com
$69

Noctua NH-U12P CPU Heat Sink (Socket 775, AM2, 754*,939*, 940* F*, 771*, 604*, ) - FrozenCPU.com
$69

Thermalright Ultra-120 eXtreme CPU Heatsink - (Socket 775 / AM2) - FrozenCPU.com
$65

Thermalright Ultra-120A Universal CPU Heatsink (Socket AM2 / 775 ) - FrozenCPU.com
$45+ fan <--"Best bang for buck"

Xigmatek HDT-S1283 Heat-pipe Direct Touch Universal CPU Cooler (Socket 754 / 775 / 939 / 940 / AM2) - FrozenCPU.com
$40