no need to go for ddr3 ram.ddr 2 is good.cause ddr3 rams and motherboards are expensive.check ur motherboard ready for core2duo,core2quad.if u r a gamer check ur motherboard have crossfire or sli support facilities.if u r a gamer and using ati cards go 4 crossfire motherboard.if u r a gamer and using nvidia cards go 4 sli motherboard if u r going 2 use 2 vga cards.check about warranty periods also.
Go for Intel,MSI,ASUS,Abit,Foxconn motherboards.(my personal favorite brands. )