Yes..........Transcend can go upto 420MHz with no probs.....
What matter is that the chips they r based on...
Try to get Transcend based on Samsung UCCC chips......they can run stabily @250MHz....i.e DDR 500MHz!!...
Or the ones based on ''Hynix D43'' chips also oc well....I have those....they r rated..3 CAS latency....but I run

@2.5 stable(Prime95 & memtest) its also stable @2 (but did'nt test prime95 and memtest)...
Although I havent tried oc'ing this memory, (coz of mobo)....but i think they can go till 450+MHz......
Its better to get 512X2 .and run them in dual channel.....u will surely get better mem read/writes....
SO even it envolves memory running 20MHz slower,it dosen't matter!