I am looking at adding an EQ to my receiver and was wondering if I need to use a stereo eq or can I use a mono eq? Money is very limited and I saw an NADY GEQ 131 mono eq (31 band) for $75 shipped. Not sure when they say mono are they talking about the actual output or just that they have one set of 31 band adjustments. I am using an Onkyo TX-8211 Receiver with some large vintage speakers (Utah woofers and tweets in Karlson Boxes).