The 6x9 BA speakers are deeper with more excursion than the Kickers. They're also
2-ohm speakers, and you replaced them with 4-ohm speakers. You cut the power
output by almost 50% with the 4-ohm speaker.
The BA speakers are 50watts @ 2-ohms.
With those kickers, more than likely, you're at 25watts power output at 4-ohms.
Wiring doesn't matter, as long as it works.
You need Kicker 2-ohm replacements to keep the volume. You could have bought the
BA replacements on eBay for $70 or less.