yes, those lighting amps are sub only amps. The freq response is 50Hz to 250 HZ only and low pass only.
If you plan on doing it now, i would highly suggest getting a new amp. the 485 like power and the more you give them the happier you will be.
HT-4 is bare min i would go. Bridged does 300x2.
SYN-4 is optimum and our number one set up on a pair of 485's. We have some guys take it to the extreme and run dual SYN-2 to gain the added headroom
But most run the SYN-4 on the 485 pair.
That kenwood is a 4 ch. Same as the HT-4 or SYN-4.
So either way you will be bridging the amps into 2 ch mode. So each speaker will be on its own side bridged.
Page 6 on our SYN-4 manual shows a SYN-4 bridged on a pair of 485's. Pge 11 on the HT-4 manual