ecs motherboard are usually a bit crap IMO (hypocritical from someone with an asrock maybe, but still true) and a microatx will limit any upgrades you may want to make in the future.
And id go for a 250gb hard disk they only cost a little extra (about a fiver here in u.k. and i think the samsung ones use 2x 125g platters, where 200gb ones use 100gb platters which are supposedly slightly slower (though i very much doubt you would be able to notice the difference)
Also here in the u.k. ive seen some retaillers selling ddr667 cheaper than ddr533 (scan, corsair xms)
Oh and dx10 cards are availible (geforce 8800gtx/gts) but you may still want to wait, they're dropping in price weekly at the moment, and when the ati's turn up they will even more
and dont know much about rosewill, but i usually avoid psu's supplied with a case theyre usually crap, and 400w is a bit weak for core2duo and dx10