Riff,
As this post is a couple of days old now, I guess you've already tried it & know the answer yourself.
If not, I would say that the CPU is capable of running your server, assuming your not too worried about what else it runs (& how quick). If its just backup - normally run during downtime & so speed is not critical, I'd have thought it would be OK.
As its really pretty quick to build the server & install SME, just get on & try it. If it doesn't prove quick enough, it's not cost you much time. If it works, great - then report back on this post & share ....
