Nice overclock. I haven't managed to get my setup stable over around 179MHz fsb, but I don't think it's the RAM, since I actually had asynchronous timings with the fsb at 166 (+33 = 199 for memory). But for some reason performance at those settings was actually quite a bit lower than with the current synchronous 161 for me. I know that the automatic PCI/AGP divider kicks in at some point (1/5). This resulted in an initial drop in performance in my rig too as I bumped up fsb +1 at a time. Oh well. 12500 is nice, and I had an 11900+ run complete before the system became to unstable (and had to reset the bios to boot after that).
If I attempted the voltage mod on the KT3Ultra's bios (involves a variable resistor, if I recall right), so that I could get 1.9 - 2.0v for the processor, I could probably hit 2GHz on this 2100+. I actually have a score for 1904MHz in the MadOnion database, which is currently my highest, at 11800+, and I managed to boot into WinXP Pro 1 time only at 2000+MHz, though my astonishment lasted only as long as it took XP to freeze entering 3DMark2k1SE (I had forgotten to decrease my multiplier by .5 as I increased the fsb another notch, resulting in the higher total MHz).
Oh well. 1845 (1846, depending on the boot, as the clock gen varies a tad) is okay, considering it's over 2200+ speeds.