I have XP1600/KR7ARAID/Corsair XMS2400 DDRAM combo.
Generally, I'd suggest incrementally upping your FSB until unstable - and then increasing VCore for stability - until higher VCore does no good. Additional Vcore over what's necessary for stability only contributes heat, and possibly more instability.
In my case, my XP1600 (AGKGA stepping) is unstable at any VCore over 1.8V, currently stable at 1.775V at 148MHz FSB. Most amd xp cpus don't have this limitation. I suspect this system would stabilize at FSB well over 150MHz with a decent cpu.
My voltages are 1.775V VCore, 2.65V DDR and 3.50V I/O.
In my case, higher DDR voltage isn't necessary. The Corsair XMS2400 dram settings are maxed, except 2T command rate for game-stability. The Corsair XMS2400 is good dram, probably overkill in a system with this poor cpu.
Hope this helps!