What you really need is a slightly newer video card (with displayport out) to take advantage of the displayport(s) on the monitor.
I think you're doing everything right, as that's how my HDMI monitor is adjusted.
Seeing as you're using an old vid card maybe you'd be better off with an older catalyst suite like 12.10 which is problem free here.
#1: Phenom II C2 955BE @ 3.6, Antec Kuhler 920, Gigabyte GA-MA790FX-DS5, Asus 5870/V2, ASUS Xonar D2X, 4 x 1gig OCZ2N1066SR2GK @800, Antec Truepower New 750, Arc Midi, Vistax64
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