Center speaker

[ace786]

Hi i,ve got a BMW E90 SE 2006 ungraded the base audio to a

Pioneer Avic F930BT Double din
Jenhert Tweeters ,Front speakers and under floor subs
Focal 165KRX2 K2 rear speakers
JL Audio HD660/4 Amp
Bavsound 10" Ultra -rigid Subwoofer with 125.2 class G amp
Audison Bit 1

My question is that i want to add a centre speaker to this setup i have a few questions to ask

1 Where to get a wiring harness for the centre speaker ??
2 should i connect it to the Bit 1 ??
3 and where should i get the power from to power the centre speaker ??

any help would be appreciated.

thank you