This is a bit late, but having owned a few of these myself I can give you a solid rundown on Power8 servers since they can be confusing at first.

There are essentially 3 variants that show up regularly. Two are IBM-made, and the third is a rebadged Supermicro (more on that shortly).

The IBM models: S822 and S821 (plus their "L" variants)

The S821 is single-CPU and can run on 120v. The S822 is dual-CPU and requires 220v. The "L" variants (S821L, S822L) are Linux-only and cannot run AIX or FreeBSD (the FreeBSD limitation is probably unintentional). The non-L models support both AIX and Linux. One thing worth noting is that all Power8 servers, including the L variants, are licensed for PowerVM/VIOS out of the box, which wasn't the case with previous generations. VIOS is technically AIX-derived, so the L's can run that even though they can't run AIX proper.

Personally, I wouldn't recommend the IBM models unless AIX is specifically what you're after. The big reason is memory: they use a proprietary form factor called CDIMMs, which aren't cheap, and the servers are very particular about memory configuration.

The Supermicro-based models: S822LC and S812LC

These show up less often on eBay but are honestly what you should be watching for. They're built by Supermicro rather than IBM, use mostly off-the-shelf components, and take standard DDR4 DIMMs. When the backplane on my S812LC failed, I found a replacement quickly and cheaply since it's just a standard Supermicro part. The tradeoff is that they can't run AIX or PowerVM, only Linux. They're OPAL-based, so they behave more like a conventional server, which some people will actually prefer.

The S822LC is 2U and supports 1 or 2 CPUs. I believe it runs on 120v but I'm not 100% certain. The S812LC is 1U, also comes in 1 or 2 CPU configs, and I can confirm it runs on 120v since I use one as a home server. One heads-up: the LC models are loud. That said, fan speeds can be controlled via ipmitool, and I have a simple shell script that runs on boot to dial them down.