I hear 2ghz with a 1700+ is a fairly mediocre goal. personally, I'm running 2415mhz (11.5*210) on my 2100+ (0310, AIUHB, the 1.6vcore one, DUT3C?) with an slk-900 and tornado (on a fanbus, duh.)
2.2ghz-2.3 on air is a good max, 2.4 is great for the 1700+ for the 2100+, 2.2ghz or so is as good as any, 2.3 or so is nearing the cap.