Also, are Hilditch and Key casual shirts a good investment? How spread are the collars on their shirts? Light, moderate, or very spread?
Depends. I have (and have seen) H&K casual shirts with button down collars and medium spread collars. Haven't seen any with a cutaway (large spread.) If you're looking for an "investment" quality shirt, Borrelli and Fray shirts can often be had for under $200 on sale in stores, and less on eBay & other discounters.