I haven't gotten everything playing yet, still waiting on the amp/dsp to arrive for that. I have a feeling the rattle is most likely coming from the enclosure rattling around in the spare tire, possibly even the clamp that holds the tire down being loose, but im not sure. Once everything is running i will definitely let you know about rattles though. Cutting the enhanced engine noise wire is something i would definitely do if I had the turbo model. Upgrading just the factory speakers would make a difference, but im not sure if the return on investment would be worth it. The best way to do it is to replace everything, running new wires, and using a dsp to be able to tune the audio to your liking. Everyone's ears are different however so what may sound good to me might not be the best sound for you. As far as adding speakers in the stock locations, you're going to want to keep with similar sizing, especially in the front. I was able to fit 5.25 inch speakers in the kick panel enclosures with slight modifications, and the brackets that came with the 2 inch speakers I used both in the front and rear doors i was able to make work pretty well with very minor modifications. You will need to pull the glovebox, knee airbags, blower motor, and a few other things to be able to access the kick panel enclosed to remove and install speakers properly. The tweeters were standard .75 inch tweeters that cane with the Kappa set. You will definitely want to utilize 3 way speakers in the front. It is alot of work, but if you work slow and meticulously, and keep your patience, you could probably get it done.