I am sorry for using the wrong typology. I thought stax calls amplifiers for energizers, no? I am looking for aftermarket amplification but find it difficult on how to approach it. any comments is much appreciated. thanks.
Got it. I was thinking of the energizer boxes, speaker amp addons to use Stax with a speaker amp.
Amp selection with high end Stax is pretty easy I think: the best you can afford! I wouldn't go below KGSSHV/KGST tier, and mjolnir-audio has a $2,300 KGSSHV these days. Above that is the KGSSHV Carbon, the best solid state you can get right now, and the Blue Hawaii SE if you want to sacrifice some bass and sound stage for uh... different mids and I believe less forward treble than at least a 22mA KGSSHV Carbon (e.g. mjolnir-audio's carbons).
You can probably get someone to build you a Grounded Grid which is a KGSSHV Carbon but with a tube output stage (4x 6CA7/EL34). It probably offers the best of both worlds between the KGSSHV Carbon and BHSE? I haven't used one myself yet.
The ultimate right now is the DIY-T2 which you can commission someone to build for you, but this is north of $10k.
Do you have a budget to work with?