Thanks, but aren't FETS more of an issue to use as a current regulator? As I understand it, an NPN transistor is basically a current amplifier (so to a point self regulating). If I was just switching then no doubt I'd use a FET but I'm never going to be saturating the base leg, just holding them in some sort of in between state, I thought transistors did this better than FETS? Also the reason I chose these transistors was because they had 125W of power dissipation available - I don't know of many FETS that cost $2 and can get rid of that much power.

It's a power supply for a laser and efficiency is not an issue. The current regulation needs to be bang on else I'll be making some very expensive bits of dust.

Thanks