Although you don't say what the problematic noise is like qualitatively (RFI? Gain device 'rush'? Induced hum? Grounding-related hum? Static-y? Same in both channels?), I'll assume with you that it's mostly some kind of induced noise because you can vary it with placement and physical shielding. Independently of one another, both your cartridge and your receiver sound like they're probably fine, although they may not be a great match for each other in terms of gain structure. But it does seem as if your step-up preamplifier may be picking up something from the immediate environment, whether or not it's also a questionable match (I'm assuming that the cables you're using fromt the step-up to the receiver are shielded). Have you tried unplugging everything else from the wall, and just listening to the step-up through the receiver, with or without the cart attached? (As far as the extra noise you hear at step #5, have you tried cupping the cart within your hands? - it could be the cart and not the TT cables.) I'd call up Kevin at KAB and tell him everything you've got and what you're hearing, I'm sure he'll be of help.
