what is going to be required for me to be able to participate in PvP without any real problems?

There's nothing official Speedy. It's been said the engine isn't graphics heavy however and that if you could run WoW, EQ, etc. you shouldn't have issue.

Will be more intensive than wow, thiking around bf2142 level gfx

Remember that you will optimally want a large viewable distance and dozens or even hundreds of ppl can be onscreen at one during a siege....

If you can, id upgrade to a ATI 4850 or better, or Nvidia 8800GT class or better and have a phenom 9000+ or core2 6600
or better.

Which is really cheap to put together nowm, relatively speaking.

If you have anything pretty modern, dual core with a 600 series+ graphics you should expect to be able to run it well~

single core i would say expect some trouble and low settings