Personally I don't think its really worth it to pay for upgrades in areas such as ram or processor power. The processor upgrades provide for only small performance changes and you can easily upgrade your ram on your own time for way less money. Furthermore, you can always buy an external monitor if you want a larger screen.
Edit: PS, paying for a large hard drive makes no sense just get an external 1 TB hard drive on the cheap and be all set for storage, period.