I'll tell Chris about your post...

But from what I understand, the -r3mix standard was the best you could get for quite a while. However, it hasn't been worked on since prior to Lame 3.91 or so.. Instead, all development has been going into the newer --alt-preset standard. There is nothing wrong with -r3mix, but you might as well switch over to standard and see if you can even notice the difference. My guess is that with most music you wont.

Chris could probably explain this better (as with other members of this board).