I bought a few t shirts in Cangs around a year ago which have been washed many times but still keep the original shape, my wife hangs them on the drying line with a clothes hanger in them so maybe thats the reason they keep their shape.
They have brand names on them Polo, Fred Perry and such like but for the price i am sure they are not original.
In the UK i used to buy size L but here i need XXL.

 

90% of my shirts are "wicking." <<Wicking fabrics are modern technical fabrics which draw moisture away from the body. They are made of high-tech polyester, which, unlike cotton, absorbs very little water. Cotton will absorb 7% of its weight in water, polyester only 0.4%.>> Polyester has come a VERY long way since "Caroline Kennedy; an unnatural fibre has never touched her body." My "round the house" shirts are sleeveless synthetic. And sorry, but I can't do anything about your existing tees.