you name the topic Video Editing Cards...
but you go on to talk about video display cards?
So I am a little confused what you want to know about.
Video editing is typically heavy 2D work. Matrox is a proven leader in Multiple display video cards. I would look to them for a video display card if the system will be used primarily for video editing. They have a new TripleHead2Go and DualHead2Go that look pretty good as well as many other options.
Video Editing Hardware cards come in all cost ranges, Matrox has a few, but their lowend cards have been out awhile. There should be some new hardware cards by Matrox probably around NAB.
If your dad is still using DV, then he might be better sticking with an all software editing suite such as Liquid Edition by pinnacle/avid.
Adobe has released Premiere Pro2 with the addition for multiple camera editing. If your dad is heavily into adding effects, whether it be sound effects or graphics it might be better for him to upgrade to a hardware accelerated option. Edius by Canopus is another software only solution or you can purchase their hardware for acceleration.
Just realize you get what you pay for, and don't by based on what a product could do, buy it because it does what you need it to do today.
To many times things are promised by any number of companies that never get fulfilled. Also if you do plan to use a Hardware accelerated card make sure that this card will work with your current system, there are motherboards that aren't compatible with hardware accelerated Video editing cards.
Your dad needs to determine what his needs are... whether it's DV... HD- HDV,HD1080i,HD720p and so on or a combination of all the formats available today.
A software solution maybe all he needs now, the more heavily you get into effects /multiple streams/layers is when a hardware solution would be most beneficial. NAB is not too far off and there should be some new products mentioned then. Another good place to readup on video related tidbits is VideoMaker magazine for average joe or DV magazine for the higher end gear.
good luck, do plenty of research and make sure the product you decide on does what you need it to do... and remember you get what you pay for pretty much with any of these products, so shop wisely.