The Rega 1000 will do well with the Shelter 501.
I think the OL Silver or Encounter would be a better sounding choice of arms. Same Rega mounting board.
You'll definitely need the VTA adjusting collar in any case. The OL arms come with it. I don't know if the Rega 1000 does or not. You may need to slightly file the armboard hole open by an additional 1/16" or so, to accomodate the VTA collar. It's an easy job.
I think the OL Silver or Encounter would be a better sounding choice of arms. Same Rega mounting board.
You'll definitely need the VTA adjusting collar in any case. The OL arms come with it. I don't know if the Rega 1000 does or not. You may need to slightly file the armboard hole open by an additional 1/16" or so, to accomodate the VTA collar. It's an easy job.