^^ do some research on the vg30s mate, they are a very good upgrade for 20s and 25s.
yes, the compressor wheel is steel, (both of mine where anyways).
My old 33 made 245rwkw on 14psi with A vg30, with supporting mods, it will do so very comfortably.
i liked it so much, i have another externally gated vg30 going on my rb20 slider