Ok...
1. I turned my computer back on
just to make this post, so you'd better read it!
2. If you haven't asked her out already - you're a fool. She's obviously interested in you.
3.
NEVER admit that you like your headphones more than her. She will never let you buy any more audio gear. In fact, never admit that you like
ANYTHING more than her.
4. Judging by your current progress, I'm going to assume that point 2 is still true. Telling her that you have a "secret" wasn't exactly the smartest thing to do IMHO, since you can't approach the subject in such a casual manner. But hey, when have men done anything right the first time?
Now that you have a "secret" to tell her, I think you should ask her to meet up with you in person (don't do anything like this over the interweb or phone - you need to see their reaction in person).
I think she will have a pretty good idea of what your secret is, so now's your chance to tell her straight out. Tell her how you feel about her - how good she makes you feel. How you couldn't tell her before because you were worried it would ruin your friendship, which is the last thing you want to do.
Show her that you can be sensitive, but also decisive and confident. However, be yourself as you'll never be able to keep up whatever false image you try to create if things go well.
I was in the same situation once and hesitated. I felt so depressed and angry at myself after I realised I had missed my chance. You will feel worse for not asking her, believe me.
I don't have much experience with this sort of thing, but I'm practically married now, so I must have done something right.