The 60gb has all the hardware... and the Emotion Engine has been disabled by a previous update. The best bet is the 80gb.

At the moment, there is no software-only emulating for PS2 games. Every PS3, except the 40gb models, still have the PS2 Graphics Synthesiser built into the motherboard, giving a mix of hardware emulation, and some software emulation.

I doubt that Sony will bother with software-only emulation for the 40gb models, simply because they want to focus more on upcoming games, and future PS3 features.