What is your receiver? I've rarely seen one that didn't have a tape monitor. The tape monitor loop is the best place to put the equalizer.
The most flexible and useful type of equalizer is a parametric equalizer, not a graphic equalizer.
With a parametric equalizer, one can adjust the center frequency for each band, rather than being stuck with fixed frequencies that may not match the frequencies you most need to adjust.
A true parametric equalizer will also allow one to adjust the width (or Q) of the band affected by each control. For the type of adjustments you hope to make, a wide band is generally more useful than the narrow bands adjusted by a graphic equalizer.
And you only need three or four bands since each band can be completely customized.
Parametric equalizers are not as common, but there are many more on the market now than there used to be. I have owned a couple, an Ashly SC-66 (which I wish I still had) and a Technics SH-9010, which I still own. Although sliders look like they might be easier to use, I find rotary controls to be much easier in practice (one reason I wish I still had the Ashly EQ).http://www.jlaudio.com/header/Support/T ... zer/287545
Look on ebay for "parametric eq" or "parametric equalizer". Sort the results by price and you may be surprised to find some that are pretty inexpensive.
If you decide to go with the more common graphic eq, try hard to get one that has no more than one octave between bands. A five band graphic eq is pretty useless. The lowest frequency should be 30hz or lower and each higher band should be no less than twice (one octave) the frequency of the one before it.
So, frequency bands of 30,60,120,240,etc. There is usually some "rounding" as frequencies go up, so actual bands will be more like 30,60,125,250,500,1000, etc..
1/3 octave equalizers are often used in professional situations because they have more resolution. But the price is much higher than for an octave eq.
There ARE stereo eqs that have one set of controls that affect both channels, but they are pretty rare. I think these are much more convenient. Especially for your use, there's no need to control the L+R channels independently. Yamaha GE-5 is one example.
Since most of your problems (and most users' problems) are in the bass, it's more important to have a lot of bands in the bass than in the treble.