Yes 242s support 400DDR. I bought 2x242 from Monarch for $203 each shipped with 60 day warranty on OEM and put them in
here Comes with both coolers so you don't need to buy any *A64 cooler won't fit anyways* and I run them@ 8x216=1.725ghz You might even squeeze 220mhz out of it but no AGP/PCI lock limits how far you can go. It has vDIMM to 2.65v and FSB/HT adjustment. It is the only Opteron board I've seen for under $300 that overclocks.
I got matching CG 242s same week less than 100 apart off the line 6weeks ago so Monarch is is a good place to get them to ensure they are as identical as possible. I've been very happy with this board and since it is ATX and takes regualr ATX PSUs I didn't have to spend anything on them either.