Old Computer into Remote Backup - Ubuntu or FreeNas?

So, I've come into the possession of two old PCs with AMD Semprons running Window's XP.  One, I plan on doing the whole PF-Sense firewall/router gig, but the other I want to turn into a remote backup/server.

Not really familiar with either Ubuntu or FreeNAS, but recommendations?  The backup machine will be kept at another property a state away, so what's the best method for remote access?  And will the Semprons do the job?

I plan to watch the Teks video on FreeNAS, but was just looking for any tips, or if there were solutions anyone liked better.  Thanks all!

I was looking into doing this recently, and came to the conclusion that to take advantage of FreeNAS with ZFS it requires a minimum of 8 GB of RAM and 64-bit architecture.

Id go with the Linux File Server (Samba?)

www.youtube.com/watch?v=-wUfzdiE4m8

I recently just did a FreeNAS server for at home and it is amazing. It was a little confusing at first because I didn't know what a lot of the settings meant, but I did figure it out. Debating whether or not to do a how to video on it... 

They recommend that you have at least 8 GB of ram for ZFS, but I tested it on a machine at work with 2 GB running 64 bit FreeNAS and it runs perfectly. 

At home I have a FreeNAS server with CIFS shares for my family, as well as the CrashPlan plugin, so we can all have a regular encrypted back up. (Very Awesome) I also am running the Plex plugin so I can have my movies, photos, and music anywhere, and it was so super easy to set up. CrashPlan is probably the hardest part of it all, but it's really easy if you know a little about linux.

Plus it's all controlled headless from my pc. (Very very awesome)