Best MC step up transformer

I am trying to find the MC transformer for my system. Now I am using Koetsu Urushi + Audio Research Phono Ref 1 with Jensen inside. The sound is pretty good but as always I wanna make it better. I've tryed to use old Koetsu MC step up trans but was unhappy about it. The sound was dull, not clear. When I've looked through ebay and audiogon, I've recognized that they are a lot of unknown for me variants (from 6k$ kondo to 100-200 $). Could you advise the best variant from quality/price point of view ?