I already have my Pioneer HU.
I need to buy Amp and speakers. (JBL 4CH will be ok? worth 3500 2nd hand)
For the subs/speakers, i have no idea on the size (10"/12") which is better setup for the amp.
I would suggest to start with seps, powered by just the HU. The Hertz ESK is a good performer that cost around 9.5k or something. I will choose Hertz over JBL because JBL's house sound tends to be shrill.