OK..........
What BigBen is refering to is that you can increase the voltage to the NorthBridge Chipset and thus probably get your FSB up a bit more. Unfortunately, this requires some soldering. Check to make sure that your Vdd/Vchipset voltage is up to its max in your BIOS, ABIT boards allow you to do that.
Also, what do you mean your 9700 sucks?!??! 373/335 is a good OC for a stock HSF on a 9700. My first card would do 380/335 but then it died (call it ritualistic suicide) and the one I have now only does 355/340 even with water! I had to do a voltage mod just to get the damn thing up to 400/340!
It does sound like you are getting near the end of your OC potential though. I suspect that if you did a light voltage mod on the chipset (to get maybe 10-15 more FSB) and then increase your CPU voltage up a bit more, you could reach your 18K goal.
You might also have to bump your memory timmings up a hair......you are starting to push the boundries of your RAM at those timmings. I am using Corsair PC3500 chips and they are set to CAS 2-2-2-3 but only running at 212FSB; at 215FSB they start to produce errors with those timmings.
The more that I think about it, it does sound like your RAM could be holding you back from higher FSB speeds. Try just focusing on higher multipliers with slight voltage increases.
Good luck and let us know.