PC4300 or PC3200

Question should I get a Corsair XMS Extreme Memory Platinum series Low latency twin pack 1GB (2X512) of DDR3200 at timing of 2 3 2 6 or say or an equivalent Mushkin PC3200 "222" special matched pair of 512's again DDR400 . Or go with say with a Kingston pair of PC4300 DDR533 pair of matched 512K Dimms?? the difference as I see it is the timings. I think that the PC3200's will run at 2 2 2 or 2 3 2 settings at clock speeds around 200Mhz or DDR 400Mhz. But to run the PC4300 I have to lower timings according to kingston to 3 4 4 8. I think if I underclocked the PC4300 to the PC3200 rates it will be really close to the PC3200 timings/settings. Any ideas or suggestions you guys can add?? or help me with??? I have been mucking around with the PC4300's (loaners) and have been unable even at Kingstons recommended sttings to reach the 533Mhz they say.
my best results with PC4300 are: setting CPU core Freq to 250 and Mem freq to 400...Which resulted in core freq 4Ghz...Mem freq 250x2 for DDR= DDR500. This comes out to a ratio 0f 1:1. That was the maximum i was able run stable.

Help with best memory to get??

I'd check and make sure that the PC4300 can run lower timings. I know some of the higher speed Mushkin ram says on their website that it can't run at lower timings because of the way it's designed to acheive a high speed.

Checked lower timings

Yes the other day I did run it at 2 2 2 6 and was not able to overclock anything at all with any stability. I am not sure right now what frequency my memory would have been operating at that point though. I was using the auto setup and just trying 10% on the asus BIOS.