CorePlayer is, I think, $20. I don't know much more about it. I don't use it myself.
My Luxo G4 is a 1GHz 7455 with 1GB of RAM and 256K L2/no L3, 167MHz system bus. I believe yours should have L3, so it should do better than mine, assuming you don't have the CPU throttled down in System Preferences.
