Thanks for the suggestions. Before the last two suggestions, the comments had leaned towards the Origin or SME. A friend cut me a sweet deal on a Sota Cosmos armboard already cut for an SME, so that swung things to the SME for me.
Last week, I picked up a used SME IV-Vi that was in good shape. I have the arm installed now, and it seems to be a good match with the Sota and Shelter 501.
It takes a couple days to really get the feel of how the arm adjustments work. I think I have it down now and have begun fine tuning.
I can already tell the arm is quiet, and pretty accurate. I like the sound already, but know I need to tweak a little more to get the best sound possible.
This arm/cartridge combo appears to have a resonance frequency of 12 hz. Ideally, this should be between 9-11hz. I used the arm dampening a slight amount to help with this.
Thanks again for the suggestions.