so i have the front right,left and center set at 80hz also the sub.the question is..if my surround and rear floorstanding speakers are rated down to 40hz should i set them that low? or should i just set them at 80hz like the fronts.

The best thing you can do is experiment with the different settings to see what sounds best. Pick one chapter of a DVD with good LFE and play it with the different settings. You will probably find that just because the speakers are rated down to 40hz, it doesn't mean they will still sound good at that point. Do you have a 60hz cutoff, or just the 40/80 (and presumably 120)? And if all else fails, depending on the type of speakers, you may be able to ask the manufacturer. I have been able to get a tremendous amount of advice on setup from Chet at Definitive Technology for my custom installation in my basement.

Some very knowledgeable forum residents have previously suggested that the best place to set the crossover is one octave above the -3dB point. In the case of speakers with a 40Hz -3dB point, that would be 80Hz. I've used this recommendation as a starting point and adjusted from there until I found the point that I liked the sound of the most.

thanks for your replies! as far as having a 60hz setting I would assume so.Since I sold my 950 faster than I thought and I figure I have 3 more weeks wait on the 990 list.I am guessing that the 990's crossover goes in 20hz increments from 40hz to 120hz,so when I finally get the chance I will experiment to find out what sounds best to me.the site sais the RS550MKII are rated 40Hz to 20KHz(±3dB)so 80hz will be may starting point.

The 990's crossover options are 40Hz, 60Hz, 80Hz, 100Hz, 120Hz, 150Hz, and 200Hz, so you should be able to tinker pretty comfortably.