id try to go with 18's, though tires are gonna be a little more expensive, especially if you do with deep dish in the rear.
the difference of price between normal and dd 18's might be something like 20$ a rim more for dd, and tires are gonna be expensive as well, if youre gonna do deep dish, you need to get a good set of rubbers for the rear, or else going wider than a 275 kinda defeats the purpose of being able to mount a 315 wide if its a **** tire. most 295-315 sizes are gonna run 250$+ per tire. though that cost can always be compensated for by using cheaper tires up front, as most that utilize a grippey deep dish setup know with dd out back you tend to have more understeer, and more than likely could care less about going in turns, as a grippey dd setup is better suited for straight line setups.
1998 Eclipse GST Spyder - 14b turbo | 3" Catback | Evo8 BoV | 170fwhp if that
2003 Redfire Cobra - 448whp/435wtq - Sold