Marantz Model 40 is a complete solution: 80 w/Ch, Streamer, DAC, FET phono stage, HEOS wireless, subwoofer manage ment impeccable build quality. I own it's little brother, the PM7000N, and it drives my LS-50s, Monitor Audio S300 7G, and Magnepan LRS all without issue. The Model 40 should provide another couple dB of headroom for you R300s.
For context I also own various Luxman, McIntosh, APT, and Adcom pieces, a VPI Prime Scout w/a Hana SH cert, and Grado and HiFiman Sansara headphones.
I also live on the Big Island half time, so I can empathize with your power issues. I strongly recommend a whole house surge protector ($200-300 installed) in addition to local power conditioning - I like full sinewave UPS.
I would also be very hesitant to invest in otherwise great gear that requires off-island service. In addition to normal wear and tear failures, Hawaii's humidity, temperature, and temperature salt corrosion are brutal on electronics. In 7 years in our new house, I've written off a refrigerator, a washing machine, and a 65" TV. Boutique manufacturers simply don't have the resources to develop and test for environmentals as major manufacturers do.
Good luck in your search!