Maximum PC

So i just finished my almost entirely new build, see below, and just went to download a HD movie from iTunes, which promptly told me that despite having this amazing new gaming rig, 3x 27" LED screens running at 1920x1080, my system was ill-equipped to play anything in HD. Am i missing something? By my count my system should be WAY over the requirements for that.....

MM Ex-U2 UFO
Asus Ramage IV Extreme
i7-3930K w/H100 cooler
G.SKILL Ripjaw Z 16GB
2x Sapphire ATI HD5870 CrossFire (Waiting for 680 Classifieds to come out)
Corsair Gold AX1200 PSU
120gb Intel 520 SSD
5x 1tb WD Caviar Blacks
1x 2tb WD Caviar Green for backup
backed up with a Smart UPS 1500
3x Samsung 27" 550 series LED

How are your monitors scaled? If you are using 3 then you should be at 5760x1080 and iTunes might have an issue with that. Have you tried running the HD content with just a single monitor attached? How are you running the monitors; HDMI? Display Port?