Valvecovers with plugs will get you the wow factor everytime... As for the BB vs SB it's gets beat to death on a regular basis. Me personally there are things I like about both setups. Both are not cheap. You really have to think about a long term goal for the car (safety upgrades, etc.) before you commit to making big power. That's my take on it. And that's why I sold my 512 besides losing interest. I wasn't interested in hacking up my car. But you may not care and if that's the case BB power will get you to the stripe pretty quick...
JW