It's hard to give you an accurate price comparison w/o a model no. but the only ones at sonicelectronix that are close to $350/pr are 1000w rms. They're $180 a pc.
The next ones down are 600w rms and they're $120 each.
I would suggest either the 15 or the 12's. Not both.
Mixing brands/sizes generally ends up being a headache and is hard to get to sound good at all. Plus, you have to spend a small fortune to get everything powered adequately. AND you have to use a LOT of cargo space because your required enclosure volume will be large.
Either way you go - a good amp and a good enclosure and either option will be loud enough to cause hearing damage if you want it to.