Short answer: unless you're trying to light it up like an operating room, I can't see a Catalina 22 having enough of a run to overload 14/2 AWG. Definitely use a tinned marine grade wire like Ancor boat cable. Marine 14 guage wire is '14 AWG' which is a slightly thicker conductor than the '14 SAE' that you'd get at wallyworld or an auto place. Additionally, the tinning on the wire keeps the copper from corroding from the ends inward.
is handy because the positive and negative conductors are carried together in a common sheath which is really convenient for hookup, identification, and mechanical strength.
Also, the ABYC recommends yellow wire(aka 'safety wire') for the ground conductor instead of black because of the prevalence of AC systems on boats now.
The 'resources' section of the BlueSea website has tables that allow you to check your total draw against the length of the run (remember that's round-trip
length) to figure maximum wire size for 10% allowable voltage drop (general) and 3% (electronics and critical equipment) but there's no escaping a bit of simple math.
Here's some reading to get you started:
Voltage Drop in Conductor - Wire Sizing Chart - Resources - Blue Sea Systems
Allowable Amperage in Conductors - Wire Sizing Chart - Resources - Blue Sea Systems
Remember too that this is for AWG wire, not SAE sizes and be sure to de-rate the wire a bit so the fuse/breaker blows long before the wire's ampacity is reached (that's your safety margin)
I'm no stereo expert, but with car stereos on boats I've found that the recommendations for speaker wiring seem meant for the comparatively shorter runs in a car - you won't regret going bigger on the power and speaker wires. My truck has 18 or 20 SAE speaker wire but the longest run is only 6'...
A 'mobile audio' forum is probably a good place to ask and they can address other stuff like noise filters and vibration damping. No offense meant to the folks here of course !