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.