I would *not* buy the Matrox card if you want to edit other than NTSC 30i or PAL 50i footage. I have the RTX100 and it's just a great system for editing 30i footage. But I'm screwed if I want to edit the 24pa from my DVX.
And there's not going to be support anytime for 24. They sell another more expensive system, the Axio, for editing 24p.
Btw - With the speed of desktops, video cards, and software (for example PPro 1.5 & 2) now it's getting to the point where you can do a lot of real-time rendering without a dedicated card. If you don't already have a fast system then I recommend testing one along with the editing package you use. See how well it works and how fast it renders. Then compare the cost of upgrading to a new system as compared to buying a card and adding to your existing system.