I had time to do a little more research on the stereo/amp/speakers, then also did some minor disassembly on my helm today. First off, I got back online and asked the Crutchfield tech some pointed questions about all of the gear they'd recommended. The new speakers and amps will definitely be a quality upgrade to the OEM Kicker system - apparently the Kicker speakers and amps Scarab put in the boats (in 2015 anyways - not sure about the newer models) were basic models, and distort at higher volumes. I hopped in the boat tonight while I was out messing around with finding the location of the amps, and verified that at high volume it does in fact distort pretty badly. And it never really gets that loud anyways - when I crank it all the way, I doubt the volume would be loud enough to be heard at all by someone being towed behind the boat on skis or a tube. The tech said that shouldn't be the case with the new setup, and at max volume he said that it shouldn't distort. He also looked up the power draw with the new setup, and he said that the stock battery/charging system should be fine with it, though he said for peace of mind, a dual battery setup wouldn't be a bad idea.
With regards to the placement of the amps, you just open the hood of the helm, remove the 6 Philips' head screws from the top of the black storage tray on the top of the helm, and the tray lifts out (just be careful to remove the weatherstripping from the one side of the tray before lifting it completely out). The amps, head unit and all of the associated wiring/connectors are fairly easily accessible under the tray, with the amps being mounted to the forward area and the head unit towards the rear. The two issues I can see right now are that the replacement amps are physically slightly larger than the OEM ones (7.8" and 8.25" in length versus 5" and 7" in length on the OEM units), and the Rockford Fosgate head unit I'm considering has a square face with a round body versus the rectangular face and body of the OEM Infinity head unit. There is actually quite a bit of room on the forward bulkhead of the helm, so I think the new amps should still fit fine, even though they'll likely require new mounting holes to be drilled (and/or a backing plate). In regards to the head unit, the Rockford head unit does still fit in the space available on the face of the helm, but the cutout for the OEM Infinity is such that I'll likely need to fabricate some sort of backing plate for the Rockford that will fill about a 3/4" gap on either side of its' faceplate that will be left by the Infinity (the Rockford's face is a bit over 4" square, where the Infinity's is a 4"x6" rectangle).
The other really cool thing about the replacement Kicker speakers is that they have an optional remote & dongle that you can wire up that allow you to control the LEDs in the speakers (i.e. multiple color choices + lightshows) versus the single color that the OEM Kickers are wired for. Apparently, the OEM Kickers actually do have the wires for the multi-color LEDs, but Scarab only connects the wires for the blue LEDs. I would imagine that if you kept the OEM Kickers and wanted a different color LED for them, you could just connect the appropriate wires for whatever color you wanted. Not clear on if you could purchase the remote & dongle and get the multi-color lightshow feature to work with the OEM setup, though.
I'm pretty close to pulling the trigger on the new gear - I'll let you know if I do, as well as how the install goes. The Crutchfield tech said that all of the wiring should be plug-and-play replacement with the new gear, so I'm cautiously optimistic that the installation should go pretty smoothly.
You'll know after trying it out for a while. Just make sure you don't accidentally drain your battery and have no solution and you're stuck on the water.