I'd really appreciate any help or advice anyone could offer regarding matching a final cut pro / final cut studio package to my Mac Pro. I've done so much research now and as soon as I think I've got it sorted, another spanner gets thrown in the works.

Firstly, Mac Pro specs:

Processor 2 x 2 GHz Dual-Core Intel Xeon

Memory 4 GB 667 MHz DDR2 FB-DIMM

Graphics NVIDIA GeForce 7300 GT 256 MB

Software Mac OS X Lion 10.7.5 (11G56)

When I bought this Mac (second hand, about 6 months ago) I'd done some research and thought I'd got one that'd allow me to edit films with nearish the minimum requirements, as I'm cheap. Then I hit the power pc problems, as obviously any FCP of a certain age can't be installed on this machine. But for FC X, which I'm not exactly tempted by anyway, my graphics card isn't good enough. (As a side note, in case this matters - in the past I've edited films directly from my external hard drive, not from the computer itself.)

I wanted some advice on how I can fit final cut pro or studio to this machine, bearing in mind I'm going to have to buy it second hand.

Would it work if I bought an older version of FCP and also bought Snow Leopard, would this install?
Or, buy a better graphics card and put up with FC X?

Two more questions, sorry: From what I can tell, FCS 2 might just work on my Mac if I bought Snow Leopard. Am I missing anything here?

And of the FCS 2 packages I've seen 2nd hand on ebay, some say 'Upgrade version' - is this something to steer clear from? Or just the same?

Sorry for the big dollop of ignorance, I had no idea this could be so complicated. Lots and lots of gratitude for any help at all!