Are the other 3 tyres OK?
If so and the wear is less than half of the tyre when new you should be alright with just one matching replacement tyre.
If the wear is more than half then I would say 2 new front tyres. But as the rears are likely to be more worn, but not due for replacement, I would advise you again replace like for like. Unless that is you have in mind a different tyre choice in mind stick with what you know and have found fine.
On mine I had tramlining issues which has been sorted by changing to Ultrac Sessantas which I am very pleaed with, but as most 370 owners seem happy with the Stones, stick with them