Although I have run wsprdaemon from the early days, before the merge feature was added., I think I only briefly used any RPi variant. At the time, I was running Odroid XU4 for other SBC projects so just built a WD system using one of those. With 8-core, 2G RAM, and 1.5+ GHz it served my 26 channels of wspr pretty well. I have two KiwiSDR/BBAI, each on its own antenna taking advantage of the merge feature. After having a fan failure, I started considering a fanless approach. Anticipating the added load of FST4 and other WD3 features, I also knew I'd need more processing power.  More MIPS without a fan could be done with a water-cooled CPU but I really wanted to keep my mains power budget low and keep my platform expense low too. My solution was the use of multiple Atomic-Pi which are X86 based, fanless, with 2G RAM, 4-core, running at 1.5GHz and 16G of on-board storage. They are about $50, you just need at add a PSU. I have 3 of them, one each for 40M, 30M, and 20M with the other bands sprinkled amongst them.   This also means no single point of failure and with some band schedule management, I can take one down for upgrade of the OS or other such task. Thus for less than $200 of platform hardware I have a fairly low power system that handles all my bands/receivers.

-Jim

WA2ZKD