Hi Guenne,
I would say the Supreme is very free blowing in comparison to the few References I have played I can't say about 7's as I have never played one but the Supreme would be a working dog, a good all round sax for pop rock jazz or classical in the same way 6's are, I would never say the Limitee is an allrounder it to me is quite niche in what it excels at, that being up close and personal or blending in an orchestra without being too loud but it would be lousy in an 80's tribute band, just totally wrong.
If you like your reference and mk7 you have nothing to lose by giving one a blow, I think you will be surprised in a good way, and only you will know what suits you.
For me I love my Mk6 but the supreme is every bit as good and more than my Mk6 with a remarkably similar tonal palate better all round intonation and just plain old fun to play I will still get my 6 out occasionally but I can't off hand think of any reason I would take it out for a gig now I have the Supreme as I honestly think the Supreme is in a new league, but that's just my 2p
Kenny