Upgrade from Densen

I'm curious if anyone has listened to Densen Audio. I have the Densen B-250 preamp and Densen B-350 mono-amps driving Wilson Sophia IIIs. What would be a significant upgrade from my current electronics?
Think you should try the Densen B-275 2-box pre - I'm just running mine in (300hrs) using an integrated in by-pass mode (as my new pwr amp is away having a fault sorted!!) and have to say it already sounds ab-fab! Just can't wait for the pwr to come back........
What is the cost in US dollars of the B-275? I'm looking to sell my Densen B-250. There appears to be few audiophiles that are familiar with Densen in the US.