Step-up transformers...

I recently purchased a lovely Benz-Micro ACE 0.4mv cart. from a member here on Audiogon, but have come to find out that my Audio Innovations 500 cannot accommodate such a low output...

I've seen/heard of a couple of options - the KAB "Pre-MC" and the "Blackhead II" (what a name, eh?)...

Has anyone ever used either one of these products? - I guess I want to use a simple step-up because it's inexpensive and I would like to stick with the tube phono pre offered by the 500.

Thanks a ton,
Mark