I put the Kumho Ecsta ASX on the rear w/ Kumho Ecsta 712 on front. I still have noise, though. Mostly because it's the wife's DD and she does not take it in for balancing very often if at all. Usually I'll get in it and hear noise and take it in, but then it's too late.
Search this forum for tires. I think some others have said they get road noise from the Kumho tires, but I don't know if they had the ASX tires or the softer 712s. I'm looking at Fazio's for the 928 because they are rated better for performance. You may want to look at ratings on
http://www.tirerack.com for noise too.