My twopenn'th:
Forks: stiffer springs and preload adjusters (if not as stock): £70-100. As for weight and oil, Guru Elmer says:
http://forums.sv650.org/viewtopic.ph...r=asc&start=15
i.e. thicker not always better. Next step would be emulators as Mike1234 says: £100.
Back end: dogbones (£15), then after that you're into new shock territory and that means ££.
Tyres: anything but stock