First of all, thanks for your comments guys.
Well, its good to me to see that every one had the same dilemma, due to the same reason. That means that I'm walking the same way that people more experineced than me.
As all of you know, the background of all of this is the money. Dive equipment, photography gear, dive trips ... are not specially chip. Nothing new for you.
Objectively, in terms of use (I've only done about 50 dives in 3 years with this gear), it seems clear that is too soon to renew. However, as has been said, shutter lag is really frustating.
I'm going to share with you an anecdote even though its a little bit humiliating to me:
First time I used my C5050 was in Tiger Beach with Jim (I suppose all of you know Jim and Tiger Beach as they are very famous on this forum). Probably is not the better site for a beginner to start to shoot, you know, to many things to control while a lot of hughe sharks are arond you. Since I wasted som dozens of pictures because I only shot in 'P' mode, some colleagues had the patience to explain to me some concepts about aperture, and shutter speed and then I was able to take som acceptable pictures. BUT, lot of times when I turn the camera after to shoot to see the picture on the screen I only found an out of focus picture of the hite sand (?). It took to me sometime to find out that what was happening is that I was turning the camera to quick after to press the sutter and the picture was taken when the camera was pointing to the bottom. 
Obviously this doesn't happen now but still I can show you some nice pictures, very well focused, first plane of the shark body but without the head ....
Jlyle, After to change to E-330, what kind of pictures were you be able to do that you cannot do before? What I really try to know is if I will expereince a big difference in case to use the 20d.
On another hand guys, how many dives or dive trip do you do at year? I'm from Spain and the average of rates for dive trips (the really good ones)is about 3000€, its difficult to me to manage enoguh budget to do more than one at year, having in account that I also like other kind of trips like land safaris, go to ski ...
Best regards
Amadeo