Thinking about a stereo upgrade

Ok, I am thinking about upgrading the stereo in my boat- not going to go freekin' crazy - just add a sub, an amp and maybe upgrade the stock Clarions.

I have a 2001 Tige with the Clarions (4) and the Clarion unit. It has the remote on the driver's side- which I want to keep. So questions:

Does this unit have outputs to an amp that I can just plug into? If so, what amp would be recommended to handle a sub and the 4 speakers? Would probably add another battery as well-

Any insight is appreciated- and PLEASE - I am not adding a set of tower speakers, multiple amps, etc- just want a better quality sound without dupming thousands into this boat. I do plan to upgrade the boat at some point, so this is just a way to suffice until I have the coin to step way up.

Thanks, Will