What do I need to install?

I have a user who wants to use IC6 and spectre.

I don't see spectre with IC6 (IC 616 installed last week).  On a different system, I see spectre installed in 6 other packages: EDI142, SPB166, SSV151, MMSIM141, INNOVUS151, ETS131.  In InstallScape, I also see SPECTRE 171 (and 181, and 191).

Which do I need?  How do I find out what I need?

Thanks,
Kyle