Good pick on the Infinity's... My recommendation is to go with 2 10"s just because 2 12s is pretty insane for our imports imho...but I guess that's up to you. As for amp, for 2 10s, I'd say up to 500watts is more than you need...you won't need anything more than that. If you really want to go all out, get a 4 channel amp (~200 watt = 50 per channel) to hook up your interior speakers...your HU will never push as much power as a good amp. Good luck!