Sorry for the break in writing, I have been doing grunt work lately as I have been wiring up a Valcom page system that integrates Via SIP to my SwitchVox phone system. It has gone great with the exception of white noise on the over head speakers.I have been working on this with Valcom and have finally found a solution to a white noise issue on my overhead Valcom speakers. It appears that the POE from the HP 5400 series chassis has a little noise in it. Normally this is a non-issue, but with speakers from the PA being run directly off the POE the white noise comes though loud and clear.
If you are doing this install I recommend smaller 1u switches from HP or 3Com as they do not present the white noise so badly.