Chakster, I had never heard of an SP20 before your post. My Googling shows a photo of something that looks like a black SP10. No outboard PS is shown in the photo, but that wouldn't necessarily mean that none was ever supplied. Does yours have an outboard supply? If yes, then it seems the SP20 was a black SP10 Mk2. If no, then I would liken it to an original SP10, not quite as great as a Mk2.
I've never tried a Micro CU500 platter mat. Nor do I even know anything about it, except that by name it would seem to have been made by Micro Seiki, out of copper. Does the "500" indicate weight, in grams? I tend to think that metal mats are of a kind, in terms of sonics. Except maybe copper sounds different from whatever alloy is used in the SAEC SS300, or stainless steel, used on the Kenwood L07D. Weight of the mat might be a factor, because one TT101-user reported that his TT101 did not like a heavy metal mat. (Perhaps the motor needed calibration; a motor that is out of calibration will exhibit subpar torque. I know this from JP's work on my TT101.) However, 500g is rather light for a metal mat. Some monsters made of copper by TTW were as heavy as 4 lbs, nearly 2 kg.
I've never tried a Micro CU500 platter mat. Nor do I even know anything about it, except that by name it would seem to have been made by Micro Seiki, out of copper. Does the "500" indicate weight, in grams? I tend to think that metal mats are of a kind, in terms of sonics. Except maybe copper sounds different from whatever alloy is used in the SAEC SS300, or stainless steel, used on the Kenwood L07D. Weight of the mat might be a factor, because one TT101-user reported that his TT101 did not like a heavy metal mat. (Perhaps the motor needed calibration; a motor that is out of calibration will exhibit subpar torque. I know this from JP's work on my TT101.) However, 500g is rather light for a metal mat. Some monsters made of copper by TTW were as heavy as 4 lbs, nearly 2 kg.