Can't Overclock my 9800Pro

I am new to overclocking, but have been visiting many sites to try to understand what is happening with my 9800Pro. It doesn't seem to overclock well at all. ATI Tool will only take it to 405 clock speed. If I try to go higher, I get sparkling on the Rhino in 3d Mark 03 and very choppy performance. I have a Flower Master Fan Controller, with a temperature sensor mounted on the back of the card behind the GPU. I'm using Artic Silver 5, and the coolers listed below. My CPU temperature goes to 38 C (according to Core Center). My Hard Drive to 38 C, my case to 28 C, my GPU to 63 C.(all according to the Fan Controller Sensors. I want to flash to XT, I have a 360 chip, but I believe there is no point if I can't overclock to XT Stock speeds. I have tried bumping the AGP Volts to 1.6 in the Bios, but saw no change.
Do I just have a crap card, or am I missing something?

Im not sure if the vantec is enough to cool the card properly. A vga silencer would be a better choice IMO. Will your memory do 365? If not then you might need some ram sinks. As always, the OC depends on the card. Some people can OC above xt speeds, some cant. Thats just the risk you take in buying a pro.

I can overclock to 405 according to ATI Tool. So, you believe that it is a heat issue then?

i agree with TxAMD.... you probably need more cooling.... also what pcb do you have? a pro or an xt? If you don't know goto this site, look at the cards and tell me which one yours looks like.....

http://www.rojakpot.com/default.aspx?location=3&var1=92&var2=0

It's a pro PCB. Man! I've been looking at other coolers, Giant Heat Pipe etc. Ugly!

cheap, easy to install cooler.... vga silencer.....

Capt Proton dont bump up your agp voltage. it doesnt help your oc and can really mess up your card