Re: 99 Jeep Stock H/U question
With that stock Infinity amp, your best off running new wiring into all the doors. I ran new wiring in my 97 ZJ with the Infinity system. I didn't run anything into the rear doors, but I did run new wiring into the front doors and into the dash as well for the tweeters. I changed out my HU for an Alpine 9855 and set it up with a PAC steering wheel adapter to keep my factory steering wheel controls, well sort of. I switched what some of the buttons do for better volume and muting options. My buttons are on the rear of the steering wheel and are not labeled so reprogramming them to do something else wasn't too big of a deal. I'd say your better off putting an aftermarket HU in there for optimal tuning options. That's my 2 cents.
94 Caprice Classic LS: DEH-P800PRS, TS-C720PRS, MRV-F545, MRD-M1005, 2 Fi X 12s in 2.5 net cubes sealed; 97 Grand Cherokee TSi: CDA-9855, TS-D1720C, active off HU power
Resident Jeep Expert, Mother Fucker