Overclocking Athlon 64 3200 (am2) on Epox mf4-ultra3

First of all, i'm a complete newbie to this o/c area. Never overclocked anything before. My Mobo doesn't let you change the memory clock multiplier. It choses one according to the CPU internal speed. Since my memory was 533mhz and the cpu is 2ghz at core, the mobo had chosen 2000/8=250 meaning 500mhz overal memory speed.

Here are the settings I can change :
Cpu Frequency [ +0 200 ]
PCIE Clock 100
Cpu Clock Ratio Auto (4 to 10)
AMD k8 Cool'n'Quiet Disable
CPU Voltage Auto
Chipset Voltage 1.5
DIMM Voltage Auto
Memory Clock Auto (has the options from DDR2 400 to DDR2 800)

I thought if i set the freg to 212 (2120mhz), the memory will be 265, near at default speed. It runs fine with just extra 120mhz. CPU-Z shows 686 as HT link.

Now, I also tried 2.4ghz but the memory gets to 300(600)mhz if Memory Clock set to Auto and HT link is 960. If I set the memory clock to DDR2 400, it comes down to 240(480)mhz. That would seem as a conservative value for memory.

I could run 3dmark2003, the CPU hit 49C with the last test. Gains just a mere 900 points over stock speeds.
The question is that I'm not sure how these settings would turn out later. Would it need any voltage changes ? Should I use memory at 240 just to be on the safe side ?