512MB of 667MHz DDR2 SDRAM (PC2-5300) on two DIMMs; supports up to 2GB
http://www.apple.com/macmini/specs.html
according to the information they have on the apple site it looks like you'll need some ddr2 ram at 667mhz and it should support the 2gigs you want
so it dosent even have to be sdram?