Thank you Speedstep for this information. Are you referring to any PCIe Video Card that has an HDMI output for Video or something different where the HDMI is just used for sound. The Video card I have in the x16 slot does have HDMI out but I am only using the DVI connection to my monitor. My monitor does not have built in speakers. If I understand correctly what you are suggesting is to then remove the audio card all together which will remove excess strain on the PCI Bus.
Sorry to put another spanner in the works but I also have a dedicated audio card in the PCI Express x4 slot and the onboard audio is turned off. The only reason I did this some while back was because I needed an audio facility that has a "What you hear" setting so I could record audio off of iPlayer Radio or live radio using Audacity.
Hope I have explained this clearly. Any further advice much appreciated.