Let your CPU temperature and stability be your guide...
If your XP1700+ is a T-Bred, getting to 2000mHz is not uncommon. I've got an 1800+ T-Bred on a KT333 mobo (EPoX 8K5A2+) that I have run at 200 x 10.0 multiplier, and in very cold weather even pushed it to 2100mHz, albeit at 1.90 vcore. This T-Bred default vcore is 1.50, and I'm running it at 1.80, with a ThermalRight AX-7 HS/80mm Sunon 50 cfm fan). CPU temps rarely exceed 44°C; mobo/case temps rarely exceed 28-29°C. This is at 100% CPU output, running SETI@home commandline client)
If you are not running a T-Bred, then I don't know what to say, except that my very first line still holds true.