I haven't touched the AGP bus but it sounds like I should set that at 66Mhz, right
I'm not sure about the A7N8X Dlx, but on my Epox 8RDA+ I <i>did</i> have to manually set it to 66Mhz. Leaving it on auto might end up running your AGP @ ~80Mhz (@ 200FSB), which would definitely be a problem, as that's well out of spec.
Decrease the multiplier a bit (10x? 9x?) if your Barton isn't locked (unless you bought it very recently it should be unlocked), so that if you hit a problem you know it's less likely to be the CPU itself, possibly RAM or something else.
Like I said, pop the FSB straight up to 180 and see if it's ok. run some stress testing stuff (I generally use Sisoft Sandra burn-in & run 3dMark looping simultaneously) for a good 20 minutes (the longer the better). If it's not crashed after a while, increase the FSB by a bit (5Mhz?) And test again. repeat.
When you hit a problem, try <i>slightly</i> increasing your CPU Vcore. Don't increase your Vcore over about 1.8-1.85V though - that should be more than enough for a decent overclock (my XP1700+ is running @ 2.25Ghz (196x11.5) on 1.575V, so you really shouldn't need much voltage, but it depends on the chip)
When you eventually find a limit you can't quite tweak around, then start fiddling with the multiplier (increase by .5, test, etc.)
Then it's really a case of just fiddling about to find the best settings. remember that better performance is obtained with a high FSB and lower multiplier (e.g. a 2000Mhz attained with 10x200FSB will be faster than the same speed attained with 12x166FSB). But that said, a slightly lower FSB may allow a slightly higher multiplier which might have slightly better performance (e.g. 192x12=2304Mhz might perform very slightly better overall than 196x11.5=2254Mhz) So it's just a case of experimenting.
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