The answer to your audio question is that it will depend upon the converter. From a quick reading of the specs, it should take the DTS core of the DTS signal (assuming you are sending DTS over HDMI) and send that over S/PDIF to your receiver. You should therefore be able to get compressed 5.1-channel audio that way. Same should be true for Dolby TrueHD being converted to Dolby Digital.
My only concern is that I don't see DTS or Dolby Digital logos on the case of the converter. It may be that they are just trying not to pay licensing for the use of the logos.
In terms of crackles and pops, it's a digital signal going out HDMI. So, the converter should just get a clean HDMI signal. If your other one using HDMI doesn't have crackles and pops, then this one shouldn't either.