At 260Mhz you would probably be better off with an HTT multiplier of x3
(and you might be able to push the CPU farther, or get a better FSB
speed at an x9 multiplier). 260x4=1040HTT which is right at or above
the limit - IIRC testing has shown that the HTT has more capacity than
the memory or CPU can provide, and you only need to shoot for 800 or
so.
Also - if you've got to relax the memory timing that much you may want
to just run a memory divider and use A64Tweaker to get the right speed
once you have the CPU settings sorted.
Definitely get a copy of Prime95 and use the Torture Test for stability
- I thought I had my system stable, but started seeing a few reboots in
F.E.A.R. - sure enough the system would boot and run fine, but Prime95
wasn't stable (30mins is a good test, and it gives you a chance to
check if your CPU cooling is good enough).
Also make sure you lock the PCIe/AGP/PCI bus so they aren't
overclocked.
My Opteron 144 is now stable @ 2.7Ghz . (300x9, HTTx3)

HTH,
Kendt