Hello all. Long time lurker, first time poster.

I picked up a '04 with the Infinity system, without Navigation, several months back. Almost as soon as I got it, the left front speaker started acting up (cutting in and out), and eventually it came to a point where nothing I could do would make it stop crackling and sloshing. I had it checked out, and the tech I took it to told me that the speaker itself was damaged, and had finally just blown completely out. He also cautioned me that since the factory amp is designed to run 8 ohm speakers, it would be potentially damaging to hook up after-market speakers, as they would overwork (and eventually blow) the factory amp. He suggested that I replace it with a factory speaker.

I gave my local Chrysler dealership a call, and it turns out that individual speakers for '04 Crossfires with the Infinity system are something like $235 per speaker.

Bearing that in mind, I've decided to go big instead of going home, so I'm replacing every speaker and adding subs. My question for the experts here on the forum is this:

Was the tech I spoke to correct? If I replace the factory speakers with aftermarket speakers (I'm using Crutchfield's "what fits my car?" feature as a guide) am I going to have to pull out the factory amp and replace the factory headunit? I'm looking at adding a nice set of Infinity components to the doors, Infinity mids behind the seats, and a powered sub of some kind in the hatch. Is a setup like this possible without losing or destroying that amp?

I've got a bit of spare money to play around with at the moment, but I'm still on a budget. If I can get the system sounding nice without having to replace the headunit (and ad a new aftermarket amp for the speakers in the doors and behind the seat) it would save me a lot of cash.

Thanks in advance for any help!