power supply question


i've changed my project for my new amp from aleph 4, to aleph 5 (heat generation problem...)... now i have a broblem choosing the trasformer: for me is very, very difficult to find a 600+VA toroidal with 25 or 30 V secondaries, i found only 500VA and i don't want to double the power supply (too expensive), do you think 500VA is enough? Any suggestion for alternative solutions?

thank you