A very quick readup on the Canopus card and the canopus page clearly states it will work with Premiere 7 (Premier Pro).
i have not used any of the the hardware listed by yourself but I have used and have got the Pinnacle DV500 Plus. That captures firewire and Analogue and produces excellent quality in both formats. You cannot capture in analogue format with Pro but can with Premiere 6.5.
I have also used the older DC30 by Pinnacle. That worked well too but does not work in XP.
So - Pinnacle hardware works very well but the software completely struggles in my humble opinion. So dont see getting studio has an advantage.
Canopus. They have an excellent name for quality both in hardware and software.
Snazzi - never used or heard much about it.
In Summary - go for the Canopus. It converts your analgue source to DV, it lock audio and video to prevent sound slip,Provides video output to a monitor or television while editing.
Pay for the quality and go for Canopus and Premiere PRo.
Let me know how you get on. This is one of my main computer interests.