From the Cypher Industries (WA) web page:
www.cypherindustries.com.au/
Toyota Soarer JZZ30 with 1JZ-GTE 2.5L Twin Turbo Engine High Flow Turbos (pair). Replacing of Ceramic Turbines with Steel Units and Larger Compressor Wheels. Comp Wheel Inducer 2mm Larger, Exducer 4mm Larger. $2,530.00
That's about the cheapest power-up you're going to get without having manifolds fabricated, going to the big single, etc.