Overclocking 6800XT

Wondering if anyone can help me out. I'm trying to overclock my XFX GeForce 6800XT 256MB AGP (I know, old card) which I've owned since January. I've gotten the core clock to 475 and the memory clock to 1170 (I believe stock was 300/1000) and it runs stable with no problems whatsoever. There is this slight problem when running certain games with the framerate lagging like a b!tch, but I think it's an issue with my cpu since it has been doing this even with my old card.

First, the temps are hitting extremely high around 75C with stock cooling. I've tried two separate aftermarket coolers, but XFX apparently doesn't make their card to standard specs and the coolers won't fit, even though they say it will fit a 6800XT. I have a case fan sucking the hot air out of that area where the card sits, but would switching it around and having it blow air onto the card help? Will changing the thermal grease on the card help?

Second, I've tried unlocking the hardware masked units for extra pipes using Rivatuner, but no such luck. In the Active pixel/vertex units configuration it says 'custom (12pp/5vp) but in the Target Adapter settings it has only the stock A2, 8pp, 4vp listed. When i click 'Customize' for the 'Allow enabling hardware masked units' option, all of the pixel and vertex units listed say 'N/A' under HW Mask (even all the ones that were originally enabled). I read somewhere that they should say either 'Yes' or 'No'. Anyone know how to enable the extra pipes and/or why the all say 'N/A'?

Any help would be much appreciated, thanks.

thanks for the help. about the temps, though, would it be better to have a fan blow onto the card or suck air from the card? It still has the stock cooler on it.

Ah, I thought that since 75C would be hot for a CPU, it would be hot for a vid card. Maybe I've got some room to push the card a little and see if it makes a difference.

And about the suggestion to buy a new card, I actually just bought this one a few months ago and I'm trying to keep my AGP system alive until I have the money to build a new one. I'm trying to do the same with my old 939 based mobo. Looking for a cheap and decent upgrade; currently running an Athlon 64 3400+, but looking at an Athlon X2 Dual Core 4200.