I have an aftermarket fairing for my RK. It has four 5" Jensen speakers, and a Jensen head unit.
Any recommendations for a better 5" speaker?
I'd go with Kicker speakers. Make sure you match the Ohm rating from the radio to the speakers. Stock Harley's are 2 Ohm but you probably have 4 Ohm speakers in your setup.
Step up to 6.5s with some adapters?
I'm pretty sure only 5" will fit. It's a Hoppe fairing.
Get you a small amp like the alpine jot-445u amp.Doesnt have a lot of power but you could use it with your speakers you have and it is very small and should fit in your fairing.and you can tap into your hot and ground on your radio because it doesn't use a lot of power. This little amp will help you more than a set of small speakers.