Harbeth vs Vandersteen vs Sonner

As Tomic601 and Bob said, you don't need a lot of wattage to drive the Vandys. The integrated amp I chose happens to have a robust amount of power output.

(((I guess my concern at the moment is whether or not that is enough power for the Treos ))) We have driven the Vandersteen Treos with a small tube amp the 20 WPC X 2 Quicksilver integrated and it works amazingly well. Because the Treos present an even Load Impedance and the amps have great output transformers. Don't hurt yourself by an assumption the unique time alignment may also win you over as it did for me.           Best JohnnyR

FYI i have the Rogue Stereo 100 driving Harbeth SHL5+ quite well.  It is not your typical 100 watt amp, it is more robust and dynamic sounding than a 150 WPC solid state amp I have.  I also comes close to the 200 watt cary audio solid state amp that the stereo 100 replaced.  huge transformers, dual mono setup, multiple power suplies and a large array of power capacitors make this one quite powerful yet still smooth, dynamic and transparent. 

@OP,
Johnny (audioconnection) is a Vandy dealer as well as a stand up guy here on Audiogon. He knows just about everything audio- and, I don't make that statement lightly.
If you want good advice, PM him. 
And, he won't try to sell you something.
I never cared for dealers until I met him.
Bob

I have the privilege of owning them paired with Rogue Audio separates
and the sound vs. the 30.2s is more open, transparent and with deeper bass response.

Avanti1960, I would agree with this. Standard SHL5+ would be my choice as well, especially since I own a pair.