for Video editing the graphics card that powers the monitor is not really that important. The power to edit video is coming from Processor, motherboard Bus speed, ram and hard drive speed. (the bigger the badder the better) The only question in a hard drive is wether the card will support Dual Monitors if that is what you are looking for.
If you are looking for PCI video cards that give you extra power to edit the video in uncompressed formats or something, that is a different story. There are cards such as the Pinnacle CineWave card which will give you some hardware boosts to edit uncompressed video. or there is a Firewire option from AJA called the I/O which can take video in from any source and capture it uncompressed or other types of formats thru the Firewire buss on the mac.
What you want to do I believe is to edit off of VHS and a mini-DV camcorder. for the camcorder all you need is a 6pin to 4pin firewire cable. For the VHS you could either loop the video thru the camcorder or buy a DV bridge from someplace like Conopus. The DV bridge is nice to feed video and audio out to your TV screen while editing though, so you can see what the picture really looks like.