Jase
Your right on the money there with avoiding fans, I found ALL fans in my remote system died with dust/corrossion. EXCEPT, the PC, oddly. I looked into fanless industrial PCs, but they are expensive and you run the real risk of an Astro app not running on it and the chances are much reduced of ferriting out a solution on unique hardware/OS version.
I ended up with a standard dual core desktop and it was very reliable, didnt hick up once, unlike all the other stuff. The fan runs very slowly and quietly, which may have helped reliability. IMO, you need to worry about fans on everything else rather than the PC and just stick with a standard known desktop.
I used this IP addressable power board, and it was very solid/reliable
http://www.digital-loggers.com/lpc.html, and cheap, only US$100 odd ! (works on 240v, but the sockets are US, a small irritation). But , as with all the gear, the fan died.