I would take a close look at your phono stage, I recently changed out some coupling caps, made all the difference in the world. If your problem is the same as mine, all the changes in setup or cartridges are not going to solve the problem. I don't know what caps the Pro-ject uses, but this is the first place I would look. You should also see if you can audition a higher quality phono stage.
My recent experience illustrates the importance of a quality phono stage. At this point I think it may be the most important link in the analog chain.