Hello - if you are planning on ordering OS X Leopard, I would ask that you consider pre-ordering it through our Amazon affiliate link. This is one of the few places that you can place a pre-order at this time.
Also, on the anti-virus front... both AVAST and AVG Free are pretty good free anti-virus solutions. Many people feel that AVG Free has too many false positives, but I have not had that experience. I am using it at home on my PC and I like it.