KT400 mobo and Barton

I am running a Barton 2500+ on a Ga-7vax mobo. I would love to be able to
overclock this cpu since the cpu is barely breaking a sweat at default
1833mhz (load temp 29-32c) . The mobo allows me to switch multipliers by
switch but the cpu seems locked at 11. Odd enough, even if I lower the
mulplier the cpu is still at 11. Its as though the cpu is ignoring the mobo
and won't even allow unerclocking.

My next step was FSB. Since I am using 512 mbkingston ddr3200 ram which
easily clocks to 400mhz, I can up the FSB to 200- except that the PCI
divider screws me up. 180is my max.

Should I get an nforce mobo? is it worthwhile? What kind of performance
increase will I realize if I up the FSB to 200 x 11 vs the current 180 x11
speed?

Thanks