Starting on the new audio system :)

RonRizz

Depends alot on your taste in music/ and your budget. The digital series are good amps for the price....The PRS are top-notch for Sound Quality. There are many others available unless your sticking with pioneer.
Door speakers are 6 1/2" and one sub or two is a preference. You only need one to produce music accurately.

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P99rs Head Unit--- Amps- 2 Pioneer Prs800d --- Zapco ST1000MX---Zapco ST-4XSQ---- SI BM mk5 Subs---SI TM65v2 Midbass--- SI M3 mids--- SI M25 xbl2 tweeters ----- 2016 MECA street class 3rd place at world finals