I've read that you can use 2T timings and they'll be ok at 400 in some cases...I have an a8n-sli delu...i have 2x512 in there now, but i don't have an extra set of the 512s to throw in with it.
Can i ask why you want 2gb? If you're going 2gb, you might as well go with 2 sticks...if only because you could then later upgrade to 4gb assuming the hardware will support that. I don't remember what the board will take off the top of my head. You might be careful there...the 1 gb sticks might not be able to run at 400 anyway...
Current machines running F@H:
AMD: [64 3500+][64 3000+][2500+][2000+][1.3x1]
Intel: [X 3.0][P4 3.0][P4 2.4x5][P4 1.4]
"...and i'm not gay" RX8 -Greatest Quote of ALL Time