do I even need a Matrox card?

Okay, I don't know too much about graphic cards and need some help here. Currently I'm working on a dual Pentium 4 3.0GHz system (1GB RAM) with a GeForce 6200 graphics card and use Adobe Premiere Pro 1.5 for editing. I capture using a Sony DSR-11 VTR through its firewire out. I also use the same VTR and firefire to connect to a video monitor for realtime previews. Now I want to get a second system but not too sure whether a Matrox really is needed here. People tell me that I MUST get at least a RTX100 Extreme Pro if I'm considering editing, but I've been doing that without a Matrox and it seems to work fine.

My question is where does the Matrox come in handy and am I overlooking a very important aspect of video editing? And should I just get a display card like the Parhalia or is a capture card an absolute essential element of editing?

Any comments / suggestions? Anyone?