Okay, let's expand it to Sonic Holography Generators, Sonic Maximizers, Range Expanders, and the like. Do you use any? If not, why? I want opinions, not fights.
I have a SAE parametric and a RS graphic equalizer. I also own a Carver S'H' Gen'. These are currently not being used because I don't have a tape mon. on my newer rcvr. I prefer hooking anything like this through the mon. than between amp/pre. You can always skip it without having to pass-thru/bypass.
EQs - Man oh, man! The last time I had my EQs hooked-up I was really happy with the way I could manipulate the sound to suit my needs. Whether it be room acoustics, speaker problems, shoddy recordings, and/or personal preference. I miss this option. I currently use my rcvrs' built in EQ to add a little 4dB+ to the lows and 2dB+ to the highs in 5.1, but nothing +/- for 2ch.
S'H'Gen' - I bought this off E-bay for $60, but haven't used it since. It makes everything sound different. Not better. Not worse. Just different. In my less than optimal conditions (10-12ft separation vs. 6ft suggested). The soundstage came up the side walls about 6ft, but the imaging fell to ****. Maybe things would be different with closer spkr placement.
BTW: If your speakers' low range is dictated by cabinetry or a passive radiator, be careful with EQs. You can put a load on a speaker (driver) that isn't made for that stong an input at that freq.