caesar, oh my that's a tough one. It's been some time now but I'll try to summarize as best I can.
Now these are my thoughts and findings in my own room and associated gear driving my MBL's so other opinons may differ. "Well I do know of numerous others who have followed and feel the same"
All of the amps offered their strenghts paired up with these speakers.
VTL Ref750's, offered lots or strengths but in comparison to others on hand I found just not a good pairing up with the MBL's. I was going to try other models but just did not materialize.
CAT Sig JL3 MK2, these were supposively designed arround the MBL's and suppose to be it. Right away you could hear the lower frequency. I did not have a CAT pre so my pairing up was with three different pre-amps I owned for many years (MBL 6010d, VTL 7.5 mk2, ARC Ref3) I then got the VAC Sig MK2a.
So I got to hear all different combos and out of the three the REF3 was my fav, did not get to really experiment much with the VAC paired up with the CAT's.
I had so many issues with my CAT amps from brand new over a years time which really was frustrating and I really never got to hear their full potential due to such.
I do allot of lower level listening, I found listening to MBL's, VTL, CAT it was okay but found you had to turn up the volume to allow them to really perform. To me if a amp can sound amazing at low volumns and offer that connection they peak my interest.
Fast forward onto the 28 SQUARED, these provided that low voloum level performance. These were my preferrence over all the above but I found that the bass seemed to be limited in comparison and just didn't sound right to me. Midrange was okay but did no way compare to the VTL's for example.
If you have MBL's and tried different amps "actually any speakers" you know there will be different characterisitcs in the actual sound it's self. Bass can sound too hard, not realistic, muddy, slow, not controlled and on. There are all kinds of bass, not just deep. You could really hear the differerences playing stand up bass, different drums with different skins and other wood instruments.
So when I had these amps as per above and trying this and that combo as mentioned, reading my notes afterwards I found I would like this or that but nothing stood out and said "this is it" so my search continued. I got that VAC pre, brand new out of the box it sounded special, something that I personally never exsperienced to such extent prior with any others and I have owned numerous. So after putting in aprox 450 hours on that pre, can't 100% recall but at this time I found myself so smitten that for the first time I sold of all my other pre-amps and was now really intregued wanting to hear the Statement 450's "hence my journey to NY" and the rest is history.
What's the chance in a life time this ever happening? well at least once because it happened.
Having the VAC paired up offers the complete package that I was looking for, opening up my wallet and has gotten me off the merry-go-round so if you are looking for a amp and pre recommendation to pair up with these wonderful MBL 101E speakers this is it, others just don't compare.
I don't want to talk negative about any of the other pces and not looking to debate, this is in my own set-up with no presure or time restraints.
If you are going to own these speakers you deserve to hear their full potential so that is my recommendation, second one over anything else that I heard is: Vac or ARC pre models I make mention, even the ARC Ref5 or Aniver paired up with the latest Bryston 28 squared using balanced IC's and just enjoy!