sm2727, If you go on Lyra site, J Carr has specific recommended range for each (I think) cart. Many people believe like Atmasphere, the higher the better. I've found this is preamp specific, and I suspect more true with tubes (also Herron)? With my AHT it gets more dynamic at 47K and more focused as resistance is lowered. There should be no change in FR. If you get noise go lower.
Regards,