Is one computer enough for this setup?

I am currently running 2 computers for my sim.

Computer 1 for controls and panels is quite old.

AMD 4000
2 GB RAM
3 cards run 5 monitors for instruments:

9800GT

7800GTX

8400 GS PCI card

Computer 2 connected via Wideview for outside visuals using Matrox Triple Head 2go:

Intel i7 3770k

16GB RAM

Nv GTX 560 ti.

Would it make more sense to put 2 more GPU's into this computer to run both outside views and panels , like a 660gtx (supports 4 monitors) and the 9800GT?

My mobo can handle the extra cards as well as my power supply.

Which of theses 2 setups would result in better performance?

BTW my sim software is the Coolsky Super 80

My other option is to build a new budget computer to replace my older one
Any thoughts?

Thanks for the help