I have a pogoplug, it's a POS...ungodly slow with next to zero RAM, unusable for most things you might want to do with it. I couldn't even rsync some files to it without setting up a damn swap drive. It went in the closet within about 15 minutes of setting it up.
As far as SBCs go, I'm a big fan of the ODROID XU4 due to its raw compute power, USB 3, and gigabit ethernet, as well as the Dragonboard 410c for its awesome mix of high speed and low power and ease of integrating into other devices.
Have you tried a distro specifically designed for small embedded systems like OpenWRT? 128MB of RAM is actually a lot for an OpenWRT device. I have a Pogoplug (modded with a second Gigabit NIC) running OpenWRT as my main router and barely even 1/4 of the RAM is in use despite being on a rather busy network.
Arch is indeed a bit resource heavy but even that has its uses. I have another Pogoplug running Arch that supervises an "experimental" altcoin mining machine. All it does is run a Python script to regularly check if the miner is working properly and restart it if it isn't. A bit of a kludge but it's the difference between a setup that I can just leave under my desk mining altcoins and a miner that needs too much attention to be worth running.