- Zu speakers at 97db may not quite be efficient enough for your 2wpc amp ( 45 tubes?). depending on the dynamics and listening level you desire of course. But you are supplementing with a sub so do you have a filter to roll off the bass to the main speakers?
- Dynaco ST 70's / Mk4 monos, etc. all have slightly rolled off top end from my experience with them. And yes mine are heavily modified. So I'd not recommend them if your missing the top end already.
- The Fisher tube amps are a better step up the vintage tube amp arena (look for an old console stereo amps they are quite good and don't have all the preamp stuff).
- Luxman tube stuff is great too ( if not going up to silly money in the used market), many others out there form the early Audio Research stuff, some select Mac's and even HH Scott gear can be really good after a rebuild. There's many choices out there just need to do some research as not everything from a specific manufacturer is great when it comes to vintage.
- SET, parallel SET, Push Pull etc many topologies all can be really good if implemented well.
- read about tube types and their associated sound signatures and pick an amp that have the tubes you like.
Also with vintage you need to consider most will require service with most likely a recap and some specific replacement parts that are known to fail or drift out of spec. So When I buy vintage gear I always add in to the cost a service call and a complete re-tube as everyone lies about tube age, ok not everyone but you get the idea you cant rely on them to be good.
Vintage gear has also gone crazy in the used market with COVID and IMO its not a good time to buy vintage right now, its a sellers market for sure. Unless you've found a holly grail of cheep gear.