Roland never wants to say that the sounds from SRX-11 are coming from Steinway, Bosendorfer or Yamaha C3... They don't to pay the "copyright". I am a big fan of piano, I tried all kind of keyboards. From Yamaha to Roland, passing through Kurzweill and Korg.
I really like Roland sound with the plus of the keyboard action which is more close than others. IMHO, Roland sound is really pure, but speaking quality of piano sound, it's also really subjective. You love or not. Whatever we say, we need to listen carefully with a high end headphone and never compare it with different monitors because the comparison will be biased by the quality of monitor. Only one high end headphone for all that makes the best comparison.

Scott, I thing you have real piano, isn't it? Let us know you opinion.

A remark, the sound expension card can be combinated with the effects on the host keyboard which gives the better sound or not (enhacement of the hammer hitting, resonance in the piano case, and reverb...)

bbc,
An owner of XV-88 with SRX11 card and G70,
And a lover of piano sound.