It really depends on your editing needs. If you are using it for editing of wedding videos on standard definitions with some transitions and video FX, a Geforce 6800 or 6600 GT is more than enough on either AGP or PCIE platform.
What is more important is your CPU and RAM specs.
As an example, I was using a Pentium 4 3.00e HT with a P875 chipset Mobo with 2GB RAM and a 6800 Graphic card and I edited a lot of dramas for RTM and ASTRO on a professional basis
Some of them are still on air now like Berarak Mendung Kelabu, Nek Nak etc....
Basically, since these video rushes were shot on BETACAM SP i just capture from a post-pro facility, edit on my pc and output the master to an external Hard Disk and then transfer to Beta SP or Digital BETA for the stations...
So i didnt get any of Pinnacle or install a capture card...for my needs they were not required at all...
Recently, I upgraded to Core2Duo simply because I am editing High Definition footages now for a singapore production...it helps to speed up rendering of video footages from the video editing timeline ...and special effects work...
You mentioned you are capturing from a DV? Well...that means you have Firewire right? That's more than enuff....you would have a pretty decent video editing rig with a Geforce 6800 or Geforce 7600.
And maybe buy additional RAMs
Hope this helps.

Added on June 1, 2007, 4:14 pmQUOTE(junkieG @ May 28 2007, 03:20 AM)
what u need is a 10k rpm hardisk on raid mode
and of course at least 4gb of ram....


Erm...that is rather high specs....unless you have tons of video streams to handle....
2GB RAM and a 320GB 7200RPM HD will just do nicely....
This post has been edited by damieneo: Jun 1 2007, 04:17 PM