I don't have any experience with HDV, but I think it uses the same 25Mbps data rate as regular DV. The trouble with HDV is that it uses heavier MPEG compression instead of the simpler compression used in DV.

I have had success capturing and editing DV with iMovie 1 (2?) on a Powermac 8500/120. I will say that my Pismo and Sawtooth are much better at editing DV.

I think the extension referenced earlier might be called the PCI Timing Extension.