The type of PC is pretty much up to you. I bought a couple of Dell’s until this last system that I had built for me by a PC guy.
There is no need for a special capture card unless you are capturing analog. In that case a Canopus AVDC card or external would suffice. Canopus used to have the DVStorm2 which worked until Premiere Pro 2.0, then Canopus decided to not support Adobe and force their users to Edius.
You can usually get by with two internal drives. One for programs and one for projects and video. A third drive for a scratch disk is handy. Forget the externals except for backup, unless your new PC has an external SATA (ESATA) port.
If you will be editing HDV, get more power and bigger drives, and probably go with a two drive RAID0 for your video.
Steven
https://www.stevengotz.com