In reverse order of (personal) preference
No Chip - £0.00
DP or Similar pre-programmed chip £30 upwards
Power Commander £350ish plus setup (no independant maps for front / rear cylinders)
FIM Ultimap Chip £150ish plus setup
Some ECU's (5.9M 2001 onwards) don't allow you to change the chip for a FIM one, so your stuck with a power commander.
FIM's are massively configurable (more so than the PC) but can also be simply dropped in place, you just don't get the full benfit of it that way.
Threaded Mode