The efficiency of your speakers may be too high for more flexibility with the output gain of the SP10. You can do two things. 1) Engage the switch on the front panel which lowers the gain of incoming signals 6db. 2)Or put in a fix attenuator, like those made by Rothwell which have 10db reduction. The benefit of this is that you will be lowing the noise floor of your SP10 - say good by to the hiss which is noticible with high efficiency speakers. I used both methods with speakers with a 92db efficiency. I got by OK with 86db speakers (+a bit of noise) by using the switch on the SP10.
Hope that helps.
Hope that helps.