If what you have with the Aria is truly "hum", then I am beginning to doubt it's due to EMI, but your story certainly is consistent with airborne interference, which usually is EMI or RFI. Except you've now revealed that you had no hum with your old turntable and phono cartridge. The problem arose when you substituted one Rega TT for another. Was the Aria situated as close to your integrated amp back then, as it is now? If so, the information about re-positioning the Aria in your room having solved the problem to some degree, is out the window. And I am getting more convinced the problem is or was due to grounding. Either your components are grounded to two or more different nodes, such that ground in one case is a few volts different from ground in another case (a ground loop, in other words), or something just isn't properly grounded.
But have we all been through a a time warp in the last 24 hours since your OP? You say now that you upgraded the Aria to a Luxman (which is indeed an excellent unit) and your problem is solved. When did you go out and buy the Luxman?
And yes, the ground lug on the back of the Aria certainly is for grounding. Millercarbon mentioned that the Aria should be grounded to house AC ground via its power cord, but that assumes you are using an IEC standard, 3-conductor power cord and that your electrical outlets are properly grounded. If you have an older home, that isn't always a valid assumption.
But have we all been through a a time warp in the last 24 hours since your OP? You say now that you upgraded the Aria to a Luxman (which is indeed an excellent unit) and your problem is solved. When did you go out and buy the Luxman?
And yes, the ground lug on the back of the Aria certainly is for grounding. Millercarbon mentioned that the Aria should be grounded to house AC ground via its power cord, but that assumes you are using an IEC standard, 3-conductor power cord and that your electrical outlets are properly grounded. If you have an older home, that isn't always a valid assumption.