I don't quite understand how you think "The table ....is immune from footfalls and airborne vibration generated by the speakers." Isolated from footfalls to a large extent but form speaker airborne vibes, now way. I have to agree with Restock that the cabinet maybe actually reinforcing low frequencies and then focusing them to the TT. If the TT was in an open situtaion the sound waves have less of a chance to be focused. Try a stethescope on the plinth or support shelf and see what your hear. You'll always have airborne vibes to contend with if your TT in in the same room as your speakers.
I would try adding a PH5. The improved phono performance btwn that and a SP16 is huge. The bass improvements alone are amazing. It's a really great sounding phonostage. I think adding a PH5 would be better than adding a LS25 simply because a good sep. phono will be better than a better preamp w/phono, not to knock a LS25.
Then a better cartridge. I think a mistake is thinking that a TT under $2K can't do a similairly priced cartridge justice. I have a friend with a HW19 MK3/RB300 I sold him my Benz Ruby2. Compared to the Denon MC and his ClearAudio MM there was no contest. Is he getting all from Ruby2 with his TT, probably not but his treble is to die for. If he added a PH5 it would sound amazing.
I would try adding a PH5. The improved phono performance btwn that and a SP16 is huge. The bass improvements alone are amazing. It's a really great sounding phonostage. I think adding a PH5 would be better than adding a LS25 simply because a good sep. phono will be better than a better preamp w/phono, not to knock a LS25.
Then a better cartridge. I think a mistake is thinking that a TT under $2K can't do a similairly priced cartridge justice. I have a friend with a HW19 MK3/RB300 I sold him my Benz Ruby2. Compared to the Denon MC and his ClearAudio MM there was no contest. Is he getting all from Ruby2 with his TT, probably not but his treble is to die for. If he added a PH5 it would sound amazing.