Either one should do a good job. I wouldn't trust your old PSU, since it is so old and you want everything to go smooth I assume. It may not be able to properly power a high end GPU from today either, if there isn't enough power on the 12v rail. On the sticker, what does it say total for the 12v rail and how many of them are there? Some have multiple rails and some have seperate rails that are shared.