BenQ G2220HD
Yes HDMi and AV cable can both be used simultaneously. I myself use similar configuration. My PS3 is hooked to dell U2311H via a HDMI to DVI cable. For the sudio part I use the AV cable and l have connected the same to my logitech Z506 using the white and red connectors. The video cable (yellow cable) is not being used.
And everything works just fine.