upgrading dual 256mb ram to 1 gig

[jojothemonkey69]

hi ok i currently have two 256 mb ram. i did a scan on crucial.com which has informed me that the ram that i currently have is DDR2. so want to upgrade to 1 gig ram now and in a few months i may upgrade to 2gig depending on performance from this ram upgrade.

so what would be best 2 x 512 or 1 gig????

thanks
Joe