Steve, You can use an equalizer with any receiver/pre-pro that has 1) a "pre-out/main-in loop", 2) a "Tape Monitor Loop, or 3) between pre-outs and an external amp.
It really doesn't affect me, since all my stuff is dinosaur (Yamaha M-80, C-80, T-80, DSP-E492, etc.), but my buddy has an Onkyo 600srx something or other receiver. He can't figure out how to hook up an equalizer.
As for me, I plug my GE-60 in the tape 1 port of the C-80 and then use the record out switch to listen to the tuner, Cd, phone, etc.
We can't figure out how to get his Onkyo to accept an equalizer.
Also, don't forget the fact that a few receivers now feature parametric EQs built-in to them which allows you to have quite a bit control over the sound.