I think a lot will depend on how they've been stored:-
Some useful info here:-
http://www.continent..._summer_en.html
Trouble is, I gues the OP will never find out, so pay your money and take your chances.
Can't comment on those as never tried them.
Reviews aren't great:-
http://www.tyrereviews.co.uk/Tyre/Dunlop/SP-Sport-Maxx-GT.htm