As Ex Pres, there is lots to change, I had an Avanti back in 1995, and upgraded this to 9 speed Daytona / Veloce in 2000, and am still using it weekly, not sure if I would go for 10 speed, or jump to 11 when it comes to replacement.
What's the big need to upgrade from what you have, as you say it is in practically new condition? From looking at the spec, you have Mirage Ergo-levers, and from memory, the nicest part of the upgrade to Daytona was loosing the Avanti Ergo-levers, which were a big stepdown from Mirage at the time.