I got my Serta iComfort at rooms to go. It's MSRP pretty much every where (around $1,200 I think) but if you shop around you'll find places who offer bonus items. I went to R2G because they had a deal where if you bought the mattress, they would toss in two of the matching pillows. Granted they were for a queen and we bought a King.. but those things are like $100 a pop. So it was worth it.
Best mattress ever. Looking back, I almost wish I had bought one of the more expensive models. It may seem like a lot of money but it's soooooo worth the investment since you spend a third of your lifespan sleeping.
***edit***
By "looking back" I mean that as, I LOVE MY MATTRESS and could only imagine how much nicer the cush upgraded model must be.