I doubt that the foam will have a really large effect on the overall sound. We should have tried it on the TTVJ Fet-A, but a goodly portion of any logic I may have had during the "meet" was washed out in my Glencairn glass. I like it better out of the AA HPA v.1.0 compared to the GSX. The TTVJ and AA have a very similar sound signature based on the short time I compared them at the "We Haz no Joe Grado" meet.
I personally have no problem with the fit of the phones but some people cannot get them to fit tight enough or without large gaps between the pads and their head which may cause problems similar to having a poor fit with the O2's. I guess I just have the next size up chosen-one head.