You're probably right, and if I put my mind to it, I can realise that sex is almost the realization of the ego. But, since sex is the only way to garanty our specie's "imortality" and perservation, it as to be more than an ego thing. Animals do it, vegetals do it... the way of doing it may be very diferent, and the reasons why "they" do it may vary a lot from "our" way, but the survival of the specie is the most important function of all living things, isnt it?
I believe that sex as we humans now it can and might be the result of our own ego, but I believe also that one can have sex for the pure act of itself.
I can understand "human" sex in two ways... sex as an act, and sex as the result of a relationship. In both ways, it can be awsome, but if you only do it for the phisical end, then you lack fellings. If you do it for the culmination of something bigger, like "love" or such, then you might go a long way after the ego problem. Even if "love" and "relationship" can be associated with egoism, and therefore, ego, ic can be more positive than negative.
If one can have sex for sex, then one can "upgrade" that action with some fellings like "love", "respect", "understandind", etc... and transform the whole act in something a lot more trancendent.
I was talking about acid and sex, and the ideia that when doing it you can change all the perception of the act, into something a lot more personal, and at the same time, more merged with the other person's personal feeling. Last time I did it, and this is just my personal opinion, with my girlfriend, we both had droped acid, and when we "melted" together, it was indescribable. Maybe if we didnt had the kind of relationship that we have, all the experience could be less transpersonal and metaphisical, but in this particular situation, we both felt "iluminated".