Alright to start it off I was thinking today that I play games, I pay for my server and I don't want to do that anymore. I have a friend whos good with setting up servers with Windows 2003 Server and I just need the box. So I want to be able to run a 32slot Day of Defeat Source 100tick server and then run a Garry's Mod 21 slot 100tick.
For a server I would recommend getting the Xeon over the Kentsfield. I have ran a game server company for some time, and thats what I can best recommend as I liked them much better on a server operating system, but I can't really comment on that as I have never ran a Kentsfield on a server operating system, but I still believe the Xeon will be better for you.
But I will be perfectly honest I dont think you will be able to run a DoD: Source & a Garry's Mod especially at a 100 tick with only that much ram, you will get into some pretty hairy spots where your players are gonna feel it.
I'll be honest I do doubt that it will work. If you cant make invest the extra 70$ for a server motherboard, then don't worry about investing into the Xeon side. The Kentsfield should work fine.
Those hard drives, I wouldn't trust those. If they came out of the original xbox I believe they are 5400 RPM drives. As you don't need much space with a game server box I would still take the step towards a little higher quality and a bit more space.
It should work fine, I don't see any issues with it not working for ya. Just out of curiosity although, whats your connection speed? Running 53 slots @ 100 tickrate isn't a cakewalk for any home-based connection.
Well if you do purchase that server box, you will then need to look into a place to put the server. If you live in a city or somewhere near a city for example, New York, not quite sure where you live, you would need to make arrangements to get rackspace from them.
You are looking at anywhere from 50$ a month to 200$ a month to get rackspace on a 100Mbit line inside a quality datacenter.