The next problem I have is how to convince my wife that I need to buy one
-dluby
i suggest you try, as best you can, to think like a woman:
first, contemplate why you need a new server. come up with sufficient reason to buy a new NAS.
next, convince yourself it is something that absolutely needs to be done in order to make things better and happier for everyone in your home. take your time getting there. this step is absolutely crucial so make sure you are completely convinced of the 'rightness' of what you want to do.
next, try having a rational discussion about the merits of upgrading and see if you can get her on the same page as you.
if that fails, wait a week...
then unplug it.
tell her it's broken. ;-)
p.s. i own two pogoplugs. i can very much recommend them. one gets used for its intended purpose the other has been rooted and reconfigured as a LAMP server. this way i can experiment with all my wordpress things before i use them to break my real website. :-))