That amp is an overpriced piece of junk that has been discontinued by Pioneer. By piece of junk I mean that it may "improve" the OE speakers (which are also crap) just because it is giving them more power, but it is noisy (74 dB S/N ratio) and doesn't provide anywhere near the usable power that they claim. If you really
have to have a compact amp that plugs into that harness and tucks into the dash, buy an Alpine, which is much better sounding:
https://www.sonicelectronix.com/item_60631_Alpine-KTP-445U.html
Here is a direct spec comparison:
https://www.crutchfield.com/S-puj8Y...nw=g&awug=1014832&gclid=EAIaIQobChMI1qbU7uec5AIVzlqGCh0PPgBoEAAYASAAEgLSt_D_BwE
If you can handle installing something under the seat or in the trunk, this is a
very high quality amp for not much money (particularly considering the sound) that will sound 10 times better than any "compact" amp:
https://www.sonicelectronix.com/item_72515_Alpine-MRV-F300.html
Since your ears are listening to the speakers (which are driven by amplifiers) replacing them is always a great first step. We just got another Jetta S manual for my son in grad school, and just replacing the factory speakers (I used Infinity Kappa coaxials) made an amazing difference.