The OM20 cartridge you are using is not really suitable for the Rega arm.The Dynavector will be a much better match and then you will begin to hear what your turntable can do.The phono stage you have is very good but obviously the more money you put into something like a phono stage the better it should get.As it stands I think you will like what you hear.Look through the archives here and you will glean much info on phono stages and matching different components.
Understanding phono stages/What to look for?
Everything from little boxes to full size components. Very few reviews. What should I look for. I have purchased a Black Cube to use with a 30 watt tube integrated. Although I have not been home yet to audition any of it. Why the huge differences in phono stages? I am using a Nottinhgham Interspace w/Rega tonearm OM20 switching soon to a Dynavector 20 low output MC. Will I want to stay with the Lehmann? Lots to learn, Louis