Paolo,
FYI - a word of caution on velocity stacks. You don't want to ride in the rain with them or leave them uncovered when the bike is not in use. Otherwise, they provide a direct route into the carburetors and intake valves to moisture and or insects. Yes, they do look cool. I started with the plastic stacks that come with the CRs, swapped them for Steel Dragon stacks, and then went to pods. I think that tuned velocity stacks will give you the best top end performance, but there is the exposure risk. It's a little bit of a pain to cover your stacks every time you bed down the bike.