New comp?

Hai guys!
So, I got this old mac pro from my family company. It is from 2008, but it got two quadcore CPUs, like this one.
I already got a 7750 (OCed 2GB) in this machine, and I was wondering if anyone would have any bearings on the benefits of another upgrade?

The CPU is supposed to be fast enough, I mean one of those cost more on amazon than my whole potential upgrade budget. I am cocerned with ram speed etc, though. The FSB is very slow, compared to that of a new mainboard.
I would love to save the money, but it seems like the RAM could become a bottleneck…

So, what do you say, wise forum?
Should I get a new top of the line GPU for this machine, or buy a completely new set up with an i7 and a mid range GPU, and upgrade the latter at a later stage?

EDIT:
Finally found some benchmarks, and I have to say that the only reason for that price, has to be that it is on backorder:p
Seems like a new cpu is in order…

That’s not very powerful, a very low-end Xeon. I would just get a new machine.

A new machine like core i7 would be a better option.