Surround sound audio card, but REW only offers stereo

[Lifespeed]

I have a surround sound audio card in a PC stereo, but REW only offers L+R selections in preferences and generator. I ran a stereo room correction, applied by pasting the filter coefficients into JRiver. The results were amazing, thanks to the software developer(s)!!
The 7.1 sound card is recognized as such by windows, which I use as 4.0 system. It sure would be nice to room-correct the surround speakers as well. Is this a problem with REW somehow not recognizing the audio card channels?

 

[John Mulcahy]

It is a limitation of Java on Windows rather than REW as such, ASIO drivers allow multichannel access. See AustinJerry's guide.

 

[Lifespeed]

Thank you, I'll report back after trying the suggested configuration.