Upgrade tonearm

Looking to upgrade my tonearm on my Sota Cosmos IV. I am currently using an SME 309 with Ortofon Kontrapunkt B cartridge. I also have a Lyra Delos and others. I do like the SME, but am considering an upgrade to get into supertable status. Considerations so far are Helius Omega, Basis Vector IV, Triplanar and Graham Phantom 2. Anything else I should consider that would work especially well on a Cosmos?
I will probably upgrade my cartridge later, so dont feel restricted to my current cartridges.

Of course, I have no opportunity to audition, so making a multi thousand dollar purchase by asking others is a little daunting, but, it is what it is.
Give the designer a call or email and ask him for suggestions. Talk to the dealer if you feel they are competent. The dealer should be able to make credible suggestions.
Sota often uses and recommends SME. There are no dealers around me. I was hoping to get input from actual Cosmos owners who have had good experiences with something other than an SME.
I have picked up a SME IV and Helius Omega. I have an Cosmos armboard for the SME, but need to send the Omega mount to SOTA to make up a Cosmos mount for it. I dont want to drill into one of my others, as they are to pretty. I have made up an oak armboard for the Omega. It sounds very nice with a Delos so I expect it will be even better with a proper Cosmos mount.
A number of years ago, I had a Helius Orion tonearm. It was the most problematic component I ever had. It went back to England a number of times, and in the end still had binding bearings. Maybe they figured it out, but for ME, I wouldn't get near a Helius arm again.