I dont run the 2000+ any more but it ran the real time previews fine, there was the odd slow down but rendering preview file of your effects speeds it up again.
A video capture card will apply certain effects to your footage using hardware so there's no need to render, it will come with its own custom effects and it will use its own miniDV codec as oposed to windowsDV codec. It may well come bundled with and optimised for Premier Pro.

256Mb of RAM is never gonna cut it for any serious editing/compositing app - Adobe states 512 as a minimum requirement to run Premier Pro. If you buy another 256 it will cost $20-30, see how you go then get another 512 if needed.

tonga