Lightspeed Sierra
I bought the Lightspeed Sierra when it was first released. I found it to be a comfortable headset with an OK rather than brilliant ANR.. Note I mainly fly C172s and Mooneys.
Mine also developed a problem early on with a loose wire causing crackling noises in one earpiece.
Anyhow I felt a little disappointed with the purchase and have recently replaced it with a Bose A20 with no regrets.
For $600 it is probably a reasonable purchase and hopefully after a few years of production, reliability has been improved. But, don't expect it to be in the same class as a Zulu or A20 when it comes to the ANR.
If you are able try and compare the two in real flight.