I dont have a Soundblaster MP3+ but have a RS SPL digital meter with RCA out and a mic from Denon used for auto room correction, so I was thinking of using the mic as input to the laptop internal soundcard via the mic input and soundcard output via the laptop headset/line out going to the AVR AUX RCA input L and R using stereo plug to split RCA L and R. I intend to try the REW using this set up and see the results. I will use the RS SPL meter to calibrate externally the input SPL level coming from the mic to calibrate the REW SPL meter. Can I use the RS SPL meter RCA out as input to the laptop internal soundcard via the mic input jack? I have tried using the Rives test cd to check the set up but not on continuous sweep on the selected frequency band. I would appreciate your comments and suggestions on this set up. I am still looking for a external soundcard maybe Soundblaster MP3+ as recommended.Thanks!