Aloha, I live on the Big Island and am much more familiar with the realities of owning electronics in this environment than most. The combination of heat, humidity, volcanic emissions and salt are not like anything anywhere on the mainland. Thing corrode and fail here that would never have those issues in other areas. For that reason alone I would avoid the smaller esoteric brands. They simply lack the resources to design and test in these extremes, and in addition, service, if needed means shipping to the mainland - a couple hundred dollars anyway. That all said, I would put my money on a Marantz. A PM7000N, which is a 60/90 W/ch streaming amp with superior build quality and a full feature set, including phono, analog, digital, Ethernet and WiFi, as well as bass management for proper subwoofer setup. This is available for under $1000 from Crutchfield or Amazon, so you anavoid the hefty freight bill. Sound Quality wise, Marantz is one of the few mainstream companies who tunes their gear by ear, selecting compnents for sound quality. Marantz house sound is slightly warm, with solid bass, good dynamics and a notable lack of midrange and high end harshness. Or, read the reviews from Absolute Sound or What HIFi or any of the othe magazines who listened to it and awarded it top honors. I know your friend has a streamer already, he can keep it or compare it to the Marantz and sell it to offset the other costs. My second choice would be the NAD 368. It has a bit more power, but lacks a few other features..
You don't mention what speakers he'll be driving, but either will drive al.ost anything on the market, maybe not quite as loud .like 2-3 dB less) as a 100-200 w amp.
