First though, McCormack was a sister company to Conrad Johnson. They should be a good fit but you want to watch which CJ Preamp you get. There is one pre in particular that I can remember that could be a bit noisy. Other than that one, it is great gear.
I import Art Audio and our Conductor preamp is phenomenal. I am confident it would work very well with your McCormack gear. Depending on your needs, I have a slimmed down Simply version as well without a headphone amp or tape loop. We offer a 30 day, no questions asked return policy. If you don’t like it, send it back. Your only risk is that you have to pay return shipping and insurance to Connecticut. For that unit, it is probably less than $60.