I don't have an S60, but I just put T1-S on my Miata and I'm pretty impressed. Very nice grip.
In the US the Bridgestone S-03's are cheaper than the T1-S and they've received rave reviews, but here in Canada the S-03's are really expensive.
Come to think of it, your driving style will dictate which tires are appropriate.
One suggestion I have is to go to www.miata.net
and look at the wheel and tire forum, you'll find a ton of recommendations that suit many different types of driving styles.
Just keep in mind that prices vary by region.
In BC, I also recommend www.tiretrends.com
as that's where I bought my Toyo's.
I have no affiliation, yada yada yada ......