If you get an early 1999 or ealier 996bip you get three spoke wheels and no titanium nitride on the forks.
from 2000 onwards they had the grey/silver five spoke wheels, the frame was silver grey to match and Ti nitride on the forks. You night even get an Ohlins rear shock.
6K should buy you a 2000 or later 996
Be cafefull about the model year you are buying, so of these bike hang around in showrooms for a while, quite often the year of registration doesn't tie up wiyht the model year.
Yo get a good idea of prices/specs go tp the bike section of
www.autorader.co.uk Theres a 2000 spec 996 bip on there athe moment looks nice with termis on. 12k miles W reg, £5,500.
Ray