I'd like a host a game server for beta testing purposes. Like testing out a new map or mod. The games would be CoD1, CoDUO, CoD2, and CoD4.

Odds are the hardware would be some Nettop/ITX-like machine such as Mac Mini 2009-2010 or Shuttle XPC.

Specs would be something like:
2Ghz Dual Core
2-4GB RAM
HDD or 480GB SSD?
Discrete GPU

I'd want to remotely access the game server from upstairs Gaming PC, while the server is connected to wired Ethernet. Maybe FTP powers too, can upload game files from upstairs PC to downstairs game server.

Probably would run OpenSUSE or Fedora, unless you guys have a distro in mind better suited for the job.

I could just rent the game server/KVM VPS, but I love to tinker with computers....

Have you checked the requirements for hosting the games themselves?

I'd say a 2~4GB machine are a little light for hosting such a VM, potentially but without being familiar with those particular games and their requirements, I can't confirm it. For such a machine, a Discrete GPU would likely be wasted as servers generally do not use GPU unless they support GPGPU, which I suspect won't be the case here as I believe the game servers themselves would need to be coded for it...

Those games don't eat anymore then 1gb. But your right I should leave extra room since 64 bit OSes eat up more ram then 32 bit OSes.

As for GPU, I could get a GT 610 or GT 710 and it would be miles ahead of recommended requirements (around $40). Or if the build has mobile Geforce or Intel HD 4000 that would work too.

Fair enough, I just wouldn't get an up-to-date expensive GPU as most run of the mill servers do not/can not use them (as far as services/daemons go); If you get into super computers consisting of 1,000+ nVidia GPUs then it's a different story!

Is there anything other than the game servers you are looking to run? In regards to FTP, I'd say use SFTP instead which comes packaged with the SSH daemon, SSH is commonly used to connect to *nix boxes. If you want a graphical connection then you'd have to look at something like VNC or NX (nomachine), there are others too... some can be found at https://en.wikipedia.org/wiki/Compar...sktop_software but this is a list for more than just *nix. I would note with VNC, that you have to be careful when using this technology as it is very easy to establish unencrypted connections, many people push VNC connections over SSH tunnels to avoid this happening.

Would also like to use that computer as a NAS for backing up photos, documents and so forth.

I have used Webmin before in one of my former video game clans. They appear to support Debian, RPMs (OpenSUSE, Fedora, Mandriva), and others.

So in a nutshell:

1) Game Server
2) Redirect for Game Server (FTP download of maps/mods)
3) NAS

Fair enough, I assume you are going for an anon/guest FTP server then? Well seems all doable to me anyways.