Simply connect front channel to mid and tweeter together. Waja hu is also 4 channel just like your kenwood hu. Beware of polarities.

Waja stock speakers are 5.25” in front and 6.5” at the back.

Based on the items you’re going to install, I guess your budget is around 1k. If I were you, I would change front speaker first. Get a good speakers, as for me i will choose eton pro. Some buddies at automotive garage do offer a good price for it. Slowly, if you get extra cash go for the amp and subwoofer. Hu is the last thing to upgrade.Waja hu not so bad. Remember, using your Kenwood hu, you might lost steering –remote control functionality.