Hello there. I personally always preferred a transformer to an active step-up. I tried quite a few of them, including Fidelity Research, Audio Tecnika etc. I can only imagine that Expressive Technology is still the best, according to reviews. Could never confirm it at about $4000. I don't know what your budget is, but Koetsus deserve the best, IMHO.
Good article here:
http://www.stereophile.com/artdudleylistening/1007listen/index4.htmland Art Dudley prefers The EAR MC4 ($2000).
I currently use two: S&B TX103 copper and K&K Lundahl LL1931 based units. I think both of these are pretty good, Lundahl being a fuller sounding, more dynamic, and TX103 a bit recessed in the mids by comparison, but overall smoother. K&K will set you off around $700, used TX103 about a grand. To build your own using Silk transformers is definitely cheaper. Koetsu transformer with a Koetsu cartridge, IMHO, would be too much honey in the mids, unless some "magical" synergy happens there. I thought TX103 worked great with my Koetsu Onyx (before it met an unfortunate accidental demise). There is a huge amount of options out there today, including some well received actives from Hagerman and ZYX.
