Yeah if you want a good
BC PS3 you have to get the 60GB model, or maybe the 20GB. The only issue is that both have been discontinued and are slightly hard to find (especially new). The new 80GB PS3 is BC by emulation, which means it's BC, but does experience problems with some PS2/PS1 titles. The 40GB model dropped BC altogether, both by hardware (20/60GB), and my software (emulation, 80GB). The 40GB can
run PSOne games though.
I did a quick search on wikipedia to confirm the Wii's BC and found this
The Wii is backward compatible with all games from the previous Nintendo system, the Nintendo GameCube, due to it being based on the PowerPC, the same base as the latter. It is compatible with GameCube controllers and memory cards but not with other peripherals such as the Game Boy Player.
So basically the Wii and the GameCube use the same processor (the PowerPC), and therefore should both be 100% backwards compatible.