Actually, they're not even technically "tweeters". They're small speakers (3.5" I think). If you've got them up there, that means you've got the factory Infinity system, in which case you're going to want to bypass the factory amp if you want an aftermarket HU. I got a 6.5" component system (tweeter, mid, xover) and just removed the small dash speaker from the metal grill, and rigged up the compnent system's tweeter in it's place (ran new wiring from the dash location to the xover). The mids replaced the door speakers. Everything in factory locations, and out of prying eyes, without compromising too much sound quality.