OEM seats are often a 'save-a-buck' component for the manufacturer to minimize production costs and boost profit a bit. Don't be afraid to try something new. Repeatedly. Until you are satisfied.
That said, I don't know of any tried and true method, fitting or Ouija board method of predicting what size, shape or type of seat will make a rider comfortable.
Go to Selle Italia's website are review their fitting method and maybe Google a few others. Getting better informed as to what makes a good fit between rider, riding style and bike is a start and should get you to a point of making a more educated guess as to what to try next. The good news is you probably can't choose a worse model than what you have. The bad news is...there's about 5,000 choices on the market!
Guys on the board tell me there are these mythical bike stores that let a fellow try out seats ***** nilly and just return them for a free swap out if they don't work out. I, personally, have not come across such a store in my locale. I have run across places like Competitive Cyclist. They offer a "No Questions Asked" return policy...'if' you want to put up with the pain in the ass (pun intended) of mail order returns.
