I have not heard any system with an Atma-Sphere preamp in it. It's bound to be a great unit, the amps are justifiably famous.
What I immediately noticed comparing the Suprtek and Atma-Sphere is that there are two completely different design philosophies at work. I can't imagine that they'll sound similar. Mick certainly has opinions on what makes for a good tube preamp
The stupid posting system won't allow me to post just a link but click on the picture to go to his blog. I think you'd have to put each into your system and listen.
I think along the same lines as Mick so I ordered a Cabernet from him and I've been very happy.