FYI,adding drops also means you'll need to swap out your shifters and brake levers. I'd advise you to get a set of trekking bars:
http://www.rei.com/product/629508

You can keep your current controls,you'll get more hand positions,and it's more comfortable when you're 'in the drops' because your wrists are flat. I absolutely love the ones on my Safari.

I'm not sure what you mean about the geometry question. Are you worried drops will mess up your handling?