Are you looking to keep the unit in the marine kit/waterproof housing? if so the alpine should still fit as the kenwood would not.
Big Nate (thesack) -
second big nate on the sony.If you have the choice to purchase something I would stay away from sony as they tend to use a 2 volt signal system at best.
The alpine remote uses the same cutout as factory installed clarion remote ,just has a bigger bezel . When installing you only have to run ignition and ground to them as there are no wires that need to go to the deck. Upon the first installation of the transceiver , only programming is necessary to add an additional remote. At this point you have switched to RF and can also add RTF (http://remotesthatfloat.com/zencart
)if desired with a quick plug- in
Here are comparative remote pics Kenwood vs. alpine