Need advice about limitations of oc w/ Prophet III GF3

I've had a GF3 for abouts 3-4 weeks now i think. I got my Prophet III through and have tried my best to overclock it to the maximum, because I have a high resolution monitor and I like playing games at 1600x1200x32 at 70fps+

Unfortunately, I know I have 4.0ns ram because all Prophet III's come with them instead of 3.8ns. The thing is I think I might have an early A3 stepping core too because of my overclocking problems.
Here are my limits of overclocking...

RAM @ 460Mhz ... No problems whatsoever
RAM @ 500Mhz ... No problems whatsoever
RAM @ 505Mhz ... Minimal artifacting in memory intensive games (Tribes 2)
RAM @ 510Mhz ... Mild Artifacting in most games
RAM @ 520Mhz ... Artifacting
RAM @ 530Mhz ... Serious Artifacting
RAM @ 535Mhz ... Crash

GPU @ 200Mhz ... No problems
GPU @ 220Mhz ... No problems
GPU @ 225Mhz ... Lockups after 5-10mins of Q3
GPU @ 230Mhz ... Crash

How can I tell if I have A3 stepping? And most important of all, what can I do to increase these overclocks?

How good is the default blueorb on the Prophet III ? And how could I cool the ram more? etc etc

Go here and look at the overclocking part.
This should give you a rough idea of what to expect with your card. Gf3 gpu's are similar to intel cpus in that one may overclock better than another.
With air cooling you can not expect to gain much from overclocking the gpu as heat is not really a issue but the limitation of of the gpu itself.
The memory will overclock better with improved air cooling but the performace gain from overclocking the memory is slight unlike the gf2's where great performance increases can be achieved from overclocking the memory.
The best thing is just to overclock what you can get and be satisfied as you have the fastest video card there is right now.
You might be able to squeeze better benchmarks from trying different drivers and motherboard bios tweaks.

Placid's always a wealth of info, that's a good link, I've read that one before...

The GPU is bare bones and won't go that much higher because of memory bottlenecks that will occur at higher GPU speeds... but form what I've read, the memory overclock will improve performace greatly.

Thanks for the advise. You say that I have the fastest card on the market but I have to say two things...

1...I overclock for the sake of it. If I am given a 90Mhz Pentium Pro I will overclock it, if get given a GF3 i will overclock it.
2...I bought a GF3 for one reason. I like high resolution. Unfortunately, not all games are playable at 1600x1200x32. Quake3 is but Tribes2 isn't.