Basic EL34 and 6sn7 tube recommendation.

I have a Mystere IA-11 tube integrated amp from sister company PrimaLuna. I bought it preowned and like-new 1.3 yrs ago and enjoy it immensely. It is outfitted with Electro Harmonix EL34 and 6sn7 tubes. (Upscale Audio is the US distributor of Mystere and PrimaLuna and also an EH supplier.)

Everything is fine currently, so I enquiring if I should replace with the same EH tubes when it's time, or should I use another moderately priced brand. I have no inclination to compare and roll tubes looking for the best match. Just looking for a good solid recommendation to plug and play.

On another related issue, my amp has Primaluna's auto-bias circuitry that automatically adjusts the tube bias, so how will I know when tubes are at the point of needing replacement, unless they are burned out completely. Thanks.
Gold Lion KT77s are a real winner IMO and won’t break the bank. Very balanced from top to bottom with good slam and detail; I haven’t found better as an  EL34 type replacement.
I've been enjoying the 6550's that Upscale recently sent my way. Midrange isn't quite as beautiful as my EL34 tubes delivered but the 6550 midrange is still beautiful as hell and the 6550's give me more top, bottom and punch. (I can't remember the brand name and I ain't gonna pull one of the tubes out its socket to see if it has a maker's mark.)
Agree with tuberist about the Gold Lion KT77s in place of EL34s. I've used them in two amps, one of them a Cayin that's made in the same factory as Prima Luna amps and in a Cary Sli-80 F1. They even compared favorably to some RFT/Siemens EL34s I have.

Another GL KT-77 fan here. They're not cheap, $49.99 each, but they're a huge upgrade over EL34 and Upscale does a good job testing them.

If you're not willing to tube roll some 6SN7's, then you'll never know how good your amp can sound. You should at least roll the preamp tubes; they make a significant contribution to the sound signature.

Yet another GL KT-77 lover here to me they are indispensable, just great top to bottom sound at fair price relative to NOS EL34 variants.
Is the kt77 a direct drop in replacement for el34 on an amp w/ auto bias circuitry? May have to call Upscale when I'm ready.

Lowrider, I've been down the road of tube rolling with past systems, but don't care much about it anymore at 67 as my ears age. I just want good value and good sound without fuss.
MJC, the KT77 should be a drop in replacement but to be safe I’d call Upscale, they are tube mavens

Thank you. I think I will call Upscale Tuberist. I suspect Upscale recommended the EH tubes to replace the stock factory Chinese tubes the amp came with.
A tube that is so underrated is the JJ EL34L ...In my amp I much prefer it over the GL KT77. If you can use KT66 variants, also consider the Reissue Tungsol 7581a. Viva Tubes is where I buy my power tubes, great service.