There are 2 different hardware components involved in making animations:
The graphic card has NO influence in the rendering times - except for the “Viewport Display” option. Flamingo takes advantage of dual processors (Rhino doesn't).
We don't have any specific hardware recommendations, so you might want to ask in the Rhino newsgroup. As for Flamingo, there's a Wiki section on Performance Tuning at FlamingoPerformanceTuning.