It is better to cross over in the native format: PCM for DVD-A (or MLP) and CD, DSD (?) for SACD, analog for lps, tuner, or the analog outputs of a DVD-A/SACD player that has no internal bass management.
Yes, and if you own a DVD-A/SACD player with internal digital bass management (which more and more DVD-A/SACD players have), you're probably better off doing bass management there, than in an external analog crossover like an ICBM, if you have the choice.
time delays, DSP processing, etc. But all these things can be done with analog circuits just as well, just that it's more expensive.
Perhaps in theory. But I don't know anyone, no matter how wealthy, using pure analog circuits for DPL II or DTS processing (DSP).

[This message has been edited by Will (edited August 16, 2002).]