Which one?

I'm looking at two different Mac Pros on craigslist. Right now I'm running a 2.3Ghz Dual Core G5 with 6GB RAM.
I know you can buy the quad core and then always upgrade the ram later, but i'm wondering which one is going to better as it is right now. I use a lot of plugins, and as many as 30-50 tracks in some songs.

Here are the specs of each:

2x Xeon Dual Core 2.66GHz
15GB RAM
1.5TB+2TB+2x1TB HDDs

or

2x Xeon Quad Core 2.66Ghz
5GB RAM
300GB HDD

Both are the 2006 models and both are running OS X Lion

Thanks!

 

Both are 2.66,but one has 8 cores,and the other has 4,so I would go for the 8 core ,becuase it's cheaper for ram and storage than it is for a processor up-grade.Unless you have a line on 2 quad processors for the dual core machine.If you are running alot of VIs,you will need the ram.You don't say which DAW software you are running,and I am assuming you are going to re-mount your audio drive from the G5 into what ever new machine you purchase.