Amplifier pairing for Altec Flamencos

I am considering adding a new amplifier to try out in my current system and could use some advice on choices to consider that would be an upgrade and complimentary to  my setup.  I have a pair of Altec Flamencos modified with the Werner Jagusch crossovers and play them with my Don Sachs preamp and a Tubes 4 HiFi  ST 120 push pull tube amp. Listening source is Bluesound node 2i with Schiit Modi Multibit Dac.   I have also been utilizing an SVS SB 1000 with them. I am not positive that my current amp is affording the old Altecs the level of dynamics and resolution that they are capable of achieving. My normal avg listening level is 75db with peaks hitting low 90s db.  Though, on occasion, I will go to 11.   What amp will resolve this question? My budget for the amp new or used is up to $3500.  


I have experience with Aletec 604E that has similar sensitivity to Altec 846A.

In the mid size rooms that I had 200-300 sq feet, 300B SET has enough power. I used McIntosh MC30 monoblocks (30+ watt), Marantz 8B in triode mode (20 watt), and 300B SET (6-7 watt). I also heard 2a3 Boothed monoblocks with my speakers and they were good enough in terms of power. 

The 30 watt McIntosh MC30 sounded great with my Spendor 2/3 speakers but with super sensitive Altecs it sounded rough and not as natural and refined as a 300B amplifier. 
What is really important is that for a 300B amplifier it has to have a powerful driver tube like 6f6, 6v6 but not popular but weak 6sn7.
The strong power supply with a big and good quality capacitor.
If your room is not huge, I suggest you try Coincident Frankenstein 300b monoblocks or Aric Audio Super 300B SET. Both these amplifiers have powerful driver tubes, interstage transformers and good power supply.

Here are my two cents about Werner Jagusch crossovers.
I used my Altec 604E with the original n1500 corosvers. Then I bought Werner Jagusch crossovers. First impression was very good, but then I realised that the sound is too coloured. I bought a measuring microphone, Minidsp umik-1 and measured speakers. I saw the issues of this crossovers:
1. No frequency correction of the HF compression driver caused significant frequency drop above 4KHz.
2. First order HF compression driver crossover led to not suppressed inverted phase output of derived below crossover frequency that caused significant frequency response dip.
I decided to build a crossover based on n1500 schematics but with modern good quality parts. I got a much flatter frequency response and more importantly a much better sound.

@fjn04  Thanks for recounting your experiences and impressions and most importantly suggestions on amps to look for.

@alexberger Thank you for your very detailed account of your experience and suggestions.  This is invaluable information! I still have the original crossovers mounted on the original backs.  I may have to  reinstall them to see how they compare to the Werner Jagusch. Who did you use/ who would you suggest that I contact to build  upgraded crossovers for Flamencos? Great Plains Audio? 

@alexberger  Thanks for the Jeff Day page.  I am going to search for a new tube amp based on everyone's input and see what i can come up with.  I will try and update the post once the upgrade is made.