Do you know what audio renderer you're using or how the sound is getting there? Does your sound device support WASAPI or ASIO? These modes will override the Windows default. You can set up sound to always come out, unadulterated, in the same number of channels as the source. One way to achieve this is with JRiver, as mentioned, or MPC-HC and some configuration tweaking, or indeed any directshow player, using something like ffdshow. Really, I think most of us want what you want and we have achieved this. Take a look at ffdshow audio - it's not a player, but is used by various players, and should be able to help you achieve what you're trying to do. It would be VERY helpful if you told us which software you're using to watch these files in the first place. There are numerous guides available, and knowing which software you're using makes it a LOT easier for us to help you.
Your original question as stated was can you bitstream with your REVO. My first response answered that. I have the same REVO, so I know. Yes, you can bitstream, in a limited way, through the HDMI. AC3 and DTS can be bitstreamed up to 5.1, including DD 2.0. Lossless formats e.g. TrueHD and DTS-HD MA cannot be bitstreamed through the ION chipset. These have to be decoded and sent as LPCM, up to 7.1. They will still be lossless and have all the original info, but they have to be decoded by the REVO. So, do you see how your question doesn't mean anything if you ask 'can it bitstream?'. The response would be 'can it bitstream what?' What kind of files are you trying to play?
It can bitstream AC3 and DTS. That means the AVR has to decode these.
It cannot bitstream mp3, flac, AAC because your AVR cannot decode these natively in a video file in almost all cases. So the very notion of bitstreaming a video file with e.g. stereo mp3 audio makes no sense.
It cannot bitstream Dolby TrueHD or DTS-HD MA. The chipset doesn't support it, even if your AVR does. You can achieve exactly the same sound, though, by decoding this in the REVO and sending LPCM to the AVR. You have to use an exclusive mode such as WASAPI or ASIO to achieve this unadulterated. For DTS-HD MA, you need Arcsoft's DTSdecoder.dll installed on your system.