I think they all have ML sound, but I think here are two levels of ML. I think mine has the basic one. As you can tell, I'm not really a music nerd and don't really care. What I can say is that the system I have does a great job of playing The Dambusters and 633 Squadron whilst blasting down the autobahn at 177mph on a dawn raid.
I'm also not a driving god, so I suspect all the TVD stuff would be lost on me. It handles and goes perfectly well as standard. I had all the radar cruise stuff on my IS-F and used it once, so I have no problem without it
As for buying, anyone who specs their own brand new RC-F would be a loony, or have some trust fund to cover the depreciation. Therefore, as Martin F said, you are left with trade-offs of price, kit, mileage and condition when looking for a used one. I think I found a real bargain so put in an immediate bid when I saw it. I had constrained myself to go for Blue as a first choice, then Red, but would not want any other colour (cue abuse from the monochrome groupies), so the kit level was immaterial. (cue more abuse and gender stereotyping about girls choosing a car by colour over kit)