In all reality, if you aren't overly worried about the contents of the drives in the case of a drive failure, you could easily use a second hand pc with an extra drive or two. For example, ripping music from CDs or movies. Yes, it will be similar to using your current pc but won't have to worry about keeping the gaming rig running.
It isn't perfect as nothing cheap is but it will work.
Although, if all that you want is something basic like this, you might as well just buy a nas from somewhere like newegg