My new SID: Echofied 6581 in Stereo

I recently had been on the look for a new sid chip, mainly for a better filter because I was unhappy with the range of the filter in the two sids i already owned, and this one sounded much better! I made a cartridge with a socket for a second sid chip as an experiment, and figured out i could play both of them together rather than just have them on two separate address ranges, so I madr some stereo recordings showing that of and comparing the two of them. Heres one, the Echofied 6581 music demo! (Has 15 years really passed?)
Left- New sid (6581 21st Wk of '84)
Right- Old sid (6581 3?th Wk of '84)
The difference in stereo is mostly just noticeable with the filters being used, since that is the biggest difference with each and every chip, as well as the noise channel (running off of different RNG's?) There were just some songs I wanted to play on my old sid that just didn't sound right.. especially when melodies used the filter!
Pictures of the cartridge i made: • Post
(With the old sid i put a heat sink on it and could not remember the date code or read it full from the seller's pictures when i bought it)