well after more than a year, i finally found a headunit that i'm looking for, which is the pioneer 80prs, lots of tuning capabilities like the p99 but most importantly with its own power out to 4 channels that can be used to simple tapped onto the factory wiring while keeping the amp and speakers stock. head unit's other features aren't bad too (blutooth, iphone control)
got all the parts ready:
be doing the install on monday, hope everything goes well