I have a nice Kenwood KAC-644 4 Channel Old School Car Audio Amplifier in perfect working or and works like a champ. 

Good sounding older Kenwood 4 channel amp. Fully tested in all functional modes with no issues.
Like to manual.

archive.org/details/manual_KAC644_SM_KENWOOD_EN/page/n17/mode/2up
and
manualslib.com/manual/286554/Kenwood-Kac-644.html


This amp features selectable high or low pass crossovers for the front and rear channels. Both high and low pass crossovers are adjustable from 50 to 200 hz. You can select to use two or four channel input to run all four channels of the amp. This amp also has fa line straight output to go to another amp. 

Shipping is on me to the USA !