My amp has an adjustment called "Twin-T Bass EQ". The manual states, "Allows for up to 18dB of boost at 45Hz for the speaker outputs when turned clockwise. It cannot affect the auxilliary outputs. Use this control sparingly. Every 3dB of boost requires double the power at 45Hz."

Right now, the amp is only driving a set of components (I will be getting a sub very soon though).

I am using my factory MY05 HU and if I wanted some more "bass" from the components, should I increase the Bass on the HU and/or adjust this "Twin-T Bass EQ"?
The HU Bass is currently set to 0 and the "Twin-T Bass EQ" is at its lowest setting right now.

Lastly, I am also using the highpass crossover on the amp as well. It's currently set around 78Hz, with the highpass crossover being adjustable with a 24dB per octave slope.

 

If you arent running a sub, and your components can handle the power, turn your highpass crossover all the way down. I wouldnt use the bass boost on the amp, but instead just adjust it with your head unit.

 

That is a bass boost control (or so it sounds). It should not really affect anything, if that is indeed what it is. Most boost controls are only operational when the low pass filter is selected. (Or so I have seen).

This might play a role when you add a sub, as you will use this feature to create a "bassline" boost level for the sub.

John