Don't go for a Vortech or a Powerdyne, US sites report relaibility problems with both these units and their design means that they only produce their power at high rpm's, so you will get similar power and torque curves to a typical turbo installation.
I take it you want good useful power at low rev's, hence no turbo considerations ?
Then, look at an Eaton M60 or M90 unit, or for a more local flavour, a Terra Charger from Yella Terra, which is a modified Eaton design anyway. Be prepared to spend moochos dineros on any custom S/C installation.
Cheers,
Mitch.
PS: Have you stretched the limits of the 1G-GZE S/C first ? Fitted an overdrive pully ? Custom modded (enlarged) the outlet pipe to raise the boost from the factory 9psi to about 11 psi ?