If I were you and could afford the Giotto and Mazzer now I would buy them now. 8-)
The HX Giotto and Mazer is an upgrade from the Silvia/Rocky. Both are more capable machines than the Silvia/Rocky combo, but that is reflected in the price. Many Silvia/Rocky owners end up upgrading to the Giotto or similar HX or Dual Boiler machines.
In the end it is a decision you have to be happy with and I think talking to a site sponsor would be the next best move.