VTL Transformer Up-Grades, Worth It?

I had the newer/better output and power transformers installed on my Manley Ref250 monoblocks (2years ago) and also had them install the MIT Multicap coupling capacitors. It was a VERY VERY significant upgrade. I fully enjoyed the amps prior to the upgrade, but after the upgrade the power, bass extension, dynamics, and detail were all very much better. It wasn't as "lushy", but still retained a full harmonically developed sound, something I think these amps did very well. Very much worth it and Evanna Manley is great to deal with!!!

As most are aware, some of the Manley/VTL line are almost identical. In the case of the Ref250 (100+w/ch Triode, 250+w/ch Tetrode), I believe it is basically identical to the MB450, but rather than using 6550's as in the MB450, the Ref250 used EL34's, a lower output tube. I'm sure some parts are different as the Manley Ref250 sold for $9k/pair versus the $7k/pair for the MB-450.

At least in the current editions of those amps, there seem to be significant differences between the two brands not only in the output tube compliment, but also in the driver arrangements, as well as the output transformer designs. In addition, the VTL has a lower amount of feedback applied, and a correspondingly higher output impedance. While they might both be inspired by David Manley's original VTL designs and look quite similar, I wouldn't expect them to necessarily sound the same.

Zaikesman, agreed that they are likely diverging in design as time goes on. That said, I also find they have a familiar (family?) sound.

Have you listened to the Ref250 and the MB-450? I'd be interested in what you thought of the two amps as I was not able to listen to both in my system at the same time.