Fwiw, my P4 is only 2.0 GHz, but when I activate the 2048 sample buffer in PTLE7 (Digi002), I can run one instance of Sonoris in HQ mode and one instance of PSP Xeon in the (aux) channel fader. There is a delay (hysteresis) to the change in sound wrt changes in settings. If one moves the mouse very slowly, one can achieve results through successive approximations (left and right). How slow to respond to settings adjustments is the Weiss hardware LinPhase EQ?
Here's a real hoot: G4 as a host for a vintage quantum DAW? Last night I was doing a null test in DP3 (of all versions) between the DP3 "edl" and a "merged soundbites" version (contiguous file) of the same edited program as in the edl. It nulled perfectly, but when I added a master fader and invoked SpectraFoo (version 3 radf17) as a plug in, in order to verify the amount of nullification, the synchronization of all tracks got so out of whack that it didn't null anymore! So, if your DAW doesn't have auto latency-management (which I guess DP3 didn't (read: doesn't) have), a measurement of the goings on will affect the goings on... Just as in a quantum experiment.
Andrew