I'll give the full, boring details approach to getting it hooked up - hopefully I'll point out a setting or connection that will get you on track. First, I'd run six analog audio cables from the NS999's multichannel analog audio output to the 990's 7.1 direct input (you'll leave the left and right surround back inputs empty at the 990). I'd also run a coaxial digital cable from the 999 to the 990 for use with regular DVD's. If your display supports component video, I'd run component cables from the 999 to the 990 (going to the DVD component video input). If it doesn't support component, I'd use whatever the best video cable it does support (s-video if possible, composite if necessary) - this is because the 990 will not convert down from component to s-video or composite (although it will convert s-video and composite to component). Also keep this in mind - if you are using s-video or composite, you will need to run a separate s-video or composite cable to the 7.1 Direct's video input. If you are using component, you can use the DVD component input and don't need to make a separate run. You'll also need to connect the 990's monitor video output to the TV, of course. Once all that is done, go into the 990's menu (getting there will let us make sure the monitor video out is working, since the menu run through the OSD). Go to the first option (input config) and select the "7.1 Direct" input (bottom of the first list, just above the option to go to audio inputs). Several items on 7.1 Direct input cannot be edited (input name, audio, and surround mode), but you can select the video input. If you are using a component video cable, pick the "COMP-DVD" option. If you are using s-video or composite, you'll want to select whichever you're using. Once all that's done, you should be able to pick "7.1 Direct" and see the 999's video and hear multichannel audio. One thing to look out for with SACD, though, is that there are a significant number of SACD titles that are stereo only - make sure you've got a multichannel SACD disc as well.
Feel free to disregard all steps that you've already done and use any steps that help, and let us know if there's still a problem.