Don't sweat it. You've obviously got a non-'ultra 400' board, but you'll probably find it runs quite happily at 200Mhz (400DDR) with the barton. If you want to save money you can probably actually get a 2500+ instead and run that at 3200+ speeds.
Nforce2 chipsets are excellent overclockers.
A <i>worst</i> case scenario for you would probably be something like 190FSBx11 = ~2Ghz, but you're quite likely to be able to get beyond 2.2Ghz and 190FSB. it's just a question of fiddling with it to see. If you just make very small adjustments and then stress-test for a couple of hours or so. The exact limit depends on the individual chip.
To give an example, my XP1700+ (thoroughbred B, stock speed 1466Mhz) is happily stable at 2254Mhz (196x11.5). at the moment.
If you do decide to get a cheaper chip instead, I'd advise against a 1700+ though, as a lot of people have reported that AMD are starting to ship T-bred A chips in the Low PR numbers.
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