Good Evening Smog Monster!!!!!!!!!!!
When i was looking for mine virtually everything 996/998 wise was above book value in dealers, including some not so good examples.
Let me know year,reg,mileage and condition and i'll give you book price in morning for the thundercat.
£5k to change sounds a little bit high, though a lot depends on details/value of your bike.
Nice choice to change to, good luck.
[Edited on 11-3-2004 by bigdaftgeordie]