Turning down the mids and highs doesn't accomplish the same thing because the intermittent frequencies are unaffected and you end up with a couple broad dips in the band (e.g., Bactrian camel hump). 31 bands of eq could probably do it.

Adding a BA-63 or dBx is essentially going to do the same thing as the bass control, maybe even moreso with respect to power requirements from the amp, unless it goes to a dedicated sub.

What value cap are you looking for?