Honestly, its about 11 months since I had the mod done, so I can't recall specifically what the mod did sonically, except to say I was extremely happy with the decision to upgrade at the time. In addition to better sound, the mod added a remote and made the unit run more efficiently. The fan runs at a slower rate so it is a bit quieter. I can also tell you that when I spoke to Barrows at PS Audio he told me that the modded P500 was competitive with the newer Premier. Since I use the P500 for a speed contoler for my VPI Aries II with the dual motor flywheel, it also takes the place of an SDS. I personally thought the upgrade a wothwhile investment.