The best tonearm for Lyra Helikon SL ?

I think you're best choices here are the SME IV.Vi or V, a Graham Phantom...then maybe a Tri Planar.

Do a search on these arms...you find a few thread discussing Lyra and SME/Graham as the best choices.

I am running a Lyra Skala with a Tri Planar VII uII with great success...

I'm running the same as Jfrech...Skala mounted on the latest Tri Planar and it is a great combination. I previously had the Skala on an Ekos mk2 and it astounded me as to how much of the Skala I wasn't hearing until I installed it on the Tri Planar.

I use a Helikon on a Trans-fi Terminator linear air bearing arm. Sounds much better(and cheaper) than this cartridge mounted on my prior Graham 1.5tc and SME IV.