First of all, sounds like DIYMA
would suit you better, judging by your gear.
Second, I use the stock unit with a line driver and I've had 6 different units in the vehicle and noticed no difference in sound quality.
However, my stock unit has the 3.5mm front panel input and I've heard that most stock units are just plain garbage, so I might just be lucky.
You could try a DSP or crossover and just running your phone straight to the inputs on either via 3.5mm to RCA perhaps?
And I completely agree with not liking the looks of aftermarket units. They also are much more complicated to use. Or for that matter, harder to leave everything flat and un-altered.
Bc2000d - jvf FI BL 15" - s800/4
offerup elite expert team 2016