About using Different brands of RAM memory and Final Cut?

Hi:

I have 5GB in my Mac Pro. The original 1GB that came from factory and aditional 4GB instaled on 4 dimms of 1GB.
I have a question, I wanted to expand the memory but I can´t find anyone in Mexico that sells Super Talent, wich was the ones they sold me at the shop, anymore.

My Question are:

1) Does it matter that if I use 4Gb more of Ram in a pair of 2gb each from another brand like Kingston or should I find more Super Talent memory?

2) Would 7GB of Ram would really boost up Final Cut or I am just gona waste my money on more Ram that I don´t need?

3) If I have the older Mac Pro can it use the 4GB dimms or not?

Thanks in advance:

Daniel Sametz.

Message was edited by: Chocorito