So I've decided to tackle the sound quality issues of the stock high performance system. Overall it's not a bad system, but it's just not doing it for me in clarity, so my plan is to upgrade the speakers and add a more powerful amplifier without disturbing the factory wiring. I have all the parts on order so my next update will be the installation. Here is my parts list, so far totaling in $300 which is right on budget .
Updated 8/16/16 (over budget, but i originally did not plan for a subwoofer)
Alpine Power Pack KTP-445U 4x45w RMS @ 2ohms $70 shipped, used on ebay
JBL P660C (front) (component set, discontinued, but can be found. Very highly rated speaker, $120 on amazon)
JBL P662 (rear) (similar to the above, but in coaxial form, $80 on amazon)
SOT-045 harness ($18 ebay)
Nissan 6.5 speaker adapters found here http://www.amazon.com/Infiniti-Plast...ct_top?ie=UTF8 ($20 amazon)
Alpine MRV-M250 ($107 amazon, could have been cheaper from jet.com)
Alpine 8" type R (SBR-S8-4) ($180 on sale)
Completed system uses the high level inputs on the new amps combined with the SOT-045 harness connected to the factory amp. This results in a clean reversible install without hacking up any oem wires. I hope my research and findings can help fellow members.