Glad to be of service, 'Hookster!
Yeah mate, if you can find a meter that offers a perceived-volume option, it'd be a simple matter of settling on a level you like, running a DI loop through the Kemper and knocking yourself out.
There'd be no need to bother with fancy, schmancy filtering, white or pink noise or anything else.
I agree with Monkey 100% that a perceived volume measurement would be ideal, but I don't quite agree about the input signal (guitar versus noise). The idea of using filtered noise is to capture every note and harmonic of the guitar in one shot, not just a single chord for example. Look at Flying Heel's images, you can see the individual notes. That makes it hard to judge EQ curves IMHO.
For observing EQ curves, I'd use plain old white noise. IMHO this is the only way.
For level matching, I'd use band-pass filtered noise that represents the whole frequency range of the guitar. Regular guitar loops might work OK here, but look at Flying Heel's images again and you can see all that missing spectral content that will be there as soon as he slides up one or two frets. Might as well test with everything there that is going to be there at some point.