Will STATA and/or SPSS benefit significantly from a higher end CPU of GFX and/or the addition of an SSD or more memory?
For these type of very general questions I would strongly advise doing a Google on something like 'best laptop for the money 2013", then scan a few returns. You'll probably start to see certain models recur...check these out for more in-depth reviewing.
$500-$800 is a lot to part with so you'd need to be sure.
Of course we can list models but you'll not want to rely on this alone for a full system.