Realeased in early 99 as the R1's little brother the R6 took the 600 class by storm almost the same as the R1 did a year earlier.
By 2002 it was still unchanged save for LED rear lights and slightly less weight. The competition fought back with a sport model CBR, the K1 GSXR and kawasaki added an extra 36 cubes to their aged ZX6R. Although each bike during the course of that year was hailed by the press as an R6 beater the history books show that the R6 remained king until the following year when Kawasaki released an all new ZX636. (see PB december 2005).
A good fast 99 model R6 will beat any sports bikes from the same era in almost every respect including the legendary fireblade. Only the all conquering R1 is it's better with a more flexible engine and slightly better handling provided it's well set up, and obviously a bit more outright speed (but not that much).
The R6 is the safe option with enough power to stay with almost anything but a usable bottom end and mid-range to stay out of trouble. Brakes are same as R1 but can fade with standard pads, suspension is more basic and less adjustable (the rear shock runs out of compression adjustment even when new) with conventional forks. A steering damper is very useful if you really start upping the pace but at just generally illegal speeds stability is never a problem. Headrace bearings can klunk even when new but doesn't mean their worn and clocks can melt if left in hot sunlight for too long.
The rear shock will be dead by 15000miles if used hard, it may feel OK when stationary but a few hard miles will see the damping literally disapear. The gearbox can be prone to worn bearings at this mileage, only detectable by riding at low revs in the higher gears (say 30mph in 4th) you should just hear it and feel vibration through the pegs. It will get louder as the problem gets worse, needing an engine rebuild to cure.
R6's are still competetive bikes in club racing so still hold their money, but don't get taken in by clean bodywork. These bikes were part of the hard core for a long time, bouncing needles off rev limiters, big wheelies and general lunacy were the norm so most will have been abused although clutches are suprisingly tough for a yamaha.
Best buy would be a 2001/02 led rearlight model with sub 10000miles on the clock, a double bubble and an adjustable steering damper owned by a rich elderly gent or a girl. Don't be put off by an end can but be wary of one that has a smaller front sprocket or jet kit as it's likley to have been owned by a loon. A one tooth smaller front sprocket is one of the best mods you can do and makes wheelies a doddle.
I reckon 3 grand should bag a good one, avoid elderly high mileage examples as engines are not cheap to repair or replace yet.