I play through a Fender Bassman 150. It is a nice amp, with plenty of features and 150 watts. The problem is I don't like how the tone controls are voiced. The bass knob is ± 15dB @ 80 Hz. This is too high for me, I would rather around 40 Hz. The treble knob is ± 15dB @ 10kHz. This is also too high for me, I would rather around 4 kHz. The semi-parametric low mid is ±15dB @ 150Hz1.5kHz and the semi-parametric high mid is ±15dB @ 800Hz4kHz. These controls are far too broad for my purposes, so I can't center in on the frequencies I like to boost and cut. So, I am considering buying an Aguilar Tone Hammer or Sadowsky Outboard Preamp to use as a preamp that would go directly into the effects return jack on the back of my amp to bypass the preamp. Is this a good/bad idea? The only caution I have is setting the input gain.