P4 2.66b at 3.2ghz - stability question

System Specs are:

Pentium 4 2.66ghz (b-533fsb)
MSI 865PE Neo2-FIS2R
2 x 256mb pc3200 CAS 2.0 Geil Golden Dragon (2.5v to 3.1v)
GeforceFX 5600 128mb
36gb WD Raptor (10k spin/serial ata)
60gb Maxtor (5400spin/ata 66)
DVD Player
CD-RW
5x 80mm Case Fans
Thermaltake Spark 7 Heatsink/Fan
2 x Dual 10in Cold Cathode Blacklights
330watt Enermax Powersupply

Overclock:
2.66(133bus) to 3.2(160bus)
GPU Core Clock 325 to 360mhz
GPU Mem Clock 500 to 680mhz

Issue:
Prime 95 won't last typically 5 minuites before erroring out and or resulting in screen artifacts. 3dmark 2001/03 run with no artifacts, etc. Sandra gives good benchmarks and stress testing does not cause lockups. Playing UNreal2003 Demo with all options and Postal2 with all options is not a problem.

Possible Issues:
My Vcore reads lower than it is set. All my power settings read lower than specified when viewed in CoreCell or MSI Bios.
Vcore: 1.44v (set at 1.525v)
3.3v reads 3.2v to 3.3v
5v reads 4.9v to 5.0v
12v reads 11.0v to 11.2v

Temperatures seem to be the same at 2.66ghz as they do at 3.2ghz. The fans and heatsink keep it 55C or lower.

While running Prime95 I can hear a change in fanspeed as the tests start and stop. My fans, even CPU fan.. are run off the 4pin connectors that power hard drives. None are powered through the motherboard. At 2.66ghz I see no errors. At 3.2ghz Prime95 errors within the first few tests(5 - 30min). Also at 3.2ghz I have noticed graphic artifacts while playing freecell with Prime95 in the background.

Any suggestions? I'm worried about increasing voltage as I don't know much about these processors. What are safe temps and what is safe voltage for processor/memory/agp. I'm not interested in frying my pc. Do I need a higher capacity power supply? Is there any way to test this. As an option I have a 420 watt powersupply by the name of Turbolink. It came with my case. I'm using the 330watt enermax because I've heard it is better than the 420w i have.

I will try lowering my overclock speeds, but the computer is so close to being completly stable that I'm actually annoyed at the prospect of scaling it back.

Beyond that, how high could I expect a 2.4/800mhz to overclock? Would there be any noticable gains. I really want to run an 800mhz fsb cpu to take full advantage of my board.

Can I trust this Corecell untility? are there other programs that I could use to confirm the accuracy of this information?

thanks much