adding 2nd amp, size, channels, rca, pwr

Hi Guys,

I need to add another amp to my boat to power two 7”component speakers and possibly (depending on your advice) two tweeters.  I currently have a Kicker ZX300.1  300W Mono amp powering 2 8” subs.

1. Since I have purchased a pair of component speakers, would I benefit from hooking up my existing tweeters (1 pair) to an Amp?  Or should I just buy another amp to power the new component speakers?  ( Looks like 2 channel amps are cheaper than 4 channel)  Also, what size Amp would you recommend?

I have Kicker KS13 tweeters:
75W RMS

JL Audio M770-CCX  7” component speakers
100W RMS

2.   Is there any difference in Multi channel (4+ channel) Amps or 2 channel amps other than the number of channels they output?   Which would you recommend for me?

3.  My Kicker amp has a pair of Signal out RCA connections.  When I wire in the second amp, should I keep my existing RCAs from the headunit to the Kicker ZX300, then just add another pair of RCAs from the ZX300 outputs to the new amp?   Or should I use a “Y-adapter” and/or possibly an electronic crossover to get the RCAs to the Amps?    Keep in mind, I am not looking for a “competition system”.  Just something done right that sounds good.

4. I read online (think cruchfield) that, “You'll need a relay on the turn-on lead to protect your receiver. A relay connected to the power antenna lead draws little current from the receiver, but supplies enough power to turn on all your amps simultaneously.”   Currently, my turn on lead to the zx300 comes from an “External Amp Control” wire coming from my headunit.  (Kenwood KTS 300MR)  I currently have an unused (non-connected) “Power control/Motor Antenna Contol Wire” that is attached to my HU.   My Amp currently only powers on in the “Signal Sense Turn-On” mode.   The manual recommends these other two methods as better than what I have currently, “Remote Tune on and DC offset Turn-On”.   Do I have it configured correctly now (it works!!)?  When adding a new amp, should I configure the turn on lead differently and should I use a “relay” off the power antenna wire.

Thanks,

Ted