I personally wouldn't go with the 8040ST. It sounded thin to me compared to it's bigger brother the 8060. Or even bigger bro the 8080.
I haven't heard the STS towers so I can't comment on them.
If you have a Golden Ear dealer close to you test those as well. You owe it to yourself to listen to every speaker you can before purchasing. You may surprise yourself and find out you like something cheaper even more.