I'm fine on packed limestone trails with 32's but then I was with 28's also. I suspect you would need to go with 35/38 to detect much difference from what you have unless you feel that the 28's are quite close to wide enough. My next tires will almost certainly be Vittoria Randonneur Hypers but since they are my next tire I can't say anything about them from experience. They look great on paper and Vittoria is definitely the road less traveled here on BF.

Ken