Overclock New NVidia3/Newcastle 3000+?

Received my components from newegg yesterday afternoon and assembled. Verified via nvidia hardware monitors that the chips are remaining cool during Futuremark benchmarking with stock heatsink and fans. Will try NVidia overclocking utility next. For all looking at similar, this assembled and ran without a hitch in a couple of hours.

NVIDIA nForce3 250Gb 800MHz FSB
AMD Athlon 64 Newcastle 3000+
Wintec PC3200 CAS 3 184 pin DDR SDRAM 512MB @2.5V
NVidia GForce 5900XT@400mhz
Maxtor 7200RPM SATA 120GB Disk
Plextor 45x IDE CD ROM
RAIDMAX Case 420W Power 3x80mm Cooling

I've heard there's not much overclocking that can be done with Newcastle AMD Athlon 64 3000+ and GeForce3 5900 XT - essentially it's already been overclocked for you by the manufacturer. I'm interested in your opinion(s).

Correction, I'm getting advice to the contrary, that the Newcastles are some of the most stable overclockers (3000+ not excluded), but that the memory and video cards are not necessarily top picks for o/c.