Ecamel,
Back when I had a Proceed PMDT transport/DVD player and a ML 360S and ML32 pre-amp I actually did try a Purcell upsampler. My experience, but again this has been a couple of years ago now, was while it did make an improvement the difference was not as great as I would have expected and therefore I opted not to buy it. If I were you I would try to find a dealer that will let you borrow one and try it yourself in your own system/room. You will very quickly hear whether it is improving things or not.
Back when I had a Proceed PMDT transport/DVD player and a ML 360S and ML32 pre-amp I actually did try a Purcell upsampler. My experience, but again this has been a couple of years ago now, was while it did make an improvement the difference was not as great as I would have expected and therefore I opted not to buy it. If I were you I would try to find a dealer that will let you borrow one and try it yourself in your own system/room. You will very quickly hear whether it is improving things or not.