As mentioned above, the condition of your lens is a big factor. If you have bought a 'lot' then maybe they are not particularly clean, or maybe they have haze or fungus (quite likely if from a humid climate like Sydney). This affects image quality far more than anything else. If you are comparing perfectly clean lenses then that's another matter, and even then there may be sample variation.
I suggest you test YOUR lens and if you are satisfied then keep it, if not then seek an alternative, but don't worry too much about it unless you decide from the get-go to buy an APO-Rodagon-N or similar high end optics because the lenses you refer to will be broadly in the same ball park. It's not like comparing a 3 element lens to a 6 element lens.
By the way, most quality enlarging lenses are 6 element/4 group designs whilst the Minolta 2.8/50 is unusually a 6 element/5 group lens (see:
http://photocornucopia.com/1061.html ). Not sure how this translates print quality but chances are there is a difference (for better or worse).