What are best speakers for VTL 125 amps and 90dB ?

Best speakers in combination with VTL that I've heard is Wilson. I've heard Wilson's with Ayre, Audio Research (twice), Linn, and some others but the VTLs were incredible.

Which model of Wilson? I can say that I can't really complain about the sound of the VTL's.

Pick up a used pair of Klipsch KHorns; they are great 'rock 'n roll' speakers and work very well with the VTL 125's, especially in Triode mode...

Are Klipsch K horns good for Jazz too?

"If my amp is clipping, wouldn't the solution be a more powerful amp?"

The VTL 125 is rated at 130 watts in tetrode mode. To theoretically gain 6 dB more headroom, you'd need to go up to 780 watts. Your speakers couldn't handle that.

So let's take a look at possibly changing speakers. The Vandersteens are rated at 86 dB. In order to gain 6 dB more headroom, you'd need 92 dB efficient speakers, which are not hard to find. Going in that direction is a much more practical solution, imho.

Duke