Premium Cotton Mattress on a Platform?

I am looking to buy a premium cotton / innerspring mattress for use on a platform bed (already bought), king size. I was looking at Shifman Beau Reve from Bloomingdales, and bc of Duane rec's on Royal-Pedic, I will look at Royal-Pedic as well.

My q is whether is makes any sense to buy a very expensive mattress if I'm going to use it on a platform bed. Don't such mattresses require their matching boxspring to really get the benefits you're paying for? Our platform is not a hard wooden board, it has wooden slats that pre-tensioned up and bend down, so it may be not too much firmer than a boxspring.

Thanks in advance to Duane and any other responders.

I really don't think so. The Box Spring is for more comfort, and often in Europe they don't use them at all. I probably do about 10 % of my Royal-Pedic sales into Platform scenarios and had no complaints from customers. Unless you spend a lot of time away from home, a good mattress is one of the best things you can buy for yourself.