DISCLAIMER: I am no expert.

Some general things you probably want to look at for 250+ whp:
1. bigger injectors
2. better fuel pump
3. engine management
4. Anything that will help the engine breathe better (throttle body, p+p'd head, intake manifold, good cat-back exhaust, etc)
5. sleeved block
6. intercooler
7. boost controller
8. excellent tuning

I would not worry about the cams. As far as engine choice goes there are several options. B18B has better torque that B16 or B18C and the internals should be stout enough to hand that power. B18C has good top end but parts will be more expensive that the B18B or B16. B16 is the cheapest and lightest of these three motors and has the best flowing head (stock). However, it does have the least torque. Its the torque you really want for a daily driver. I would recommend dropping in the B18B, follow the eight
suggenstions above, and if you really want peace of mind, build the bottom end with forged pistons and rods.

Someone correct me if I have ommited or mis-stated anything.