Adcom pre amp versus Van Alstine

Go with Van Alstine.

In my experience, AVA makes great gear with excellent service.

I had an Adcom preamp in the mid 1990's and it was truly unremarkable. 

I have had an Adcom Preamp and Amplifier in my workshop for 30 years. They have been subjected to heavy dust and fumes of every variety. My house was hit by lightening and a Krell Preamp fried, but not the Adcom. They are also decent sounding and void of any ill habits. They have also been run way more than my main system, frequently 12 hours daily. I had a Van Alstine preamp in the late 70s and it was OK. I sold it for a Conrad Johnson which I thought sounded better. 

+1 @dweller I had an Adcom GTP-400 and it was "meh." AVA would be better.

This modwright is pretty nice, too: