Does anyone by any chance know what the measurable difference is between stock and port and polished heads with aggressive cams? Are we talking 3 hp? 5 hp? 10 hp........ 0.5 hp?!

Before I go spending the money i like to know its worth it, but i want this to be the first and last time the heads ever come off 3205 so i figure do it once and do it right or don't do it at all.