I think the conversionsa are nice, I haven't really seen one done really well as an all around rider though. At least not out this way. Just drag trikes or poor handling unreliable conversions. Until I see one done well (I'm sure they're out there) I'd put the money into making an existing Honda trike the best it can be with lots of mods and accessories to make it nice! I think am xr 600 conversion would be a heavy pig of a trike. In a long travel suspension frame it might be fun in the desert though!
own:
1986 250R- ported polished, carb mods, Esr atc-5 pipe and silencer
1986 250R- mild porting, carb mods (Clean!)
1985 350X- all stock (super clean!!)
1985 350x- desert project in the works
1986 250sx- Mostly stock
1985 200x- (pretty clean mostly stock)
1985 Yamaha tri zinger 60