It depends on what brand you buy. I have a Sapphire X800GTO2 that comes with the extra 4 pipelines unlocked right out of the box. Also the Sapphire card will easily overclock to near X850 XT PE speeds.
If you can find the Sapphire X800 GTO2 it's almost guaranteed to be unlocked and quite overclockable. But my understanding is that it was a limited edition card and it might not be available anymore.
the Red Sapphire X800 GTO AGP's are also pretty much a sure thing they have r430 core, i have link to a site with the custom flash for the Red Sapphire X800 GTO if you need it i will post it.
If you have the Sapphire GTO2, I have a bootable .ISO image BIOS flash you can burn to cd. Reboot with cdrom and it prompts you to unlock the 12 pipe version. Some earlier versions had only 12 pipes which were enabled with a BIOS flash.
Actually I have the cheap Powercolor, may not get anywhere with it but I don't want to spend much right now so if it gets me to next fall great. I am going to try and push it to the limits.
The Sapphire X800GTO2 has a BIOS flash which unlocks all SIXTEEN (16) pipes. I did that on mine and run a stable overlock of 525 core and 1200 ram. Good luck.
The BIOS flash (unlock additional 4 pipes for 16 total) worked fine on my Connect3D x800GTO. I think you may be out of luck with that Powercolor card. From what I remember, it was usually the Sapphire GTO2 and Connect3d GTOs that unlocked without problems.
For future reference on anybody that does a search I got a reasonable oc out of the Powercolor at 456/450 and really stable there I could run 459gpu even but knocked it down a touch. It can't be unlocked.
It is a bad performer NWN runs at below 44fps nearly all the time and my old 9700pro agp ran about 60+ most of the time with a lesser processor and 512mb of ram versus 1.5 I have now.