Audiophiles need to feel bass but commonly aren't satisfied with consumer setups. Usually high end headphones, speaker systems, DACs, and other exotic equipment are involved in the equation. The best way to feel bass in these scenarios is to let the high end amps drive the headphones and split a signal (pre or post depending on your preference) to the SubPac. This way you get a remarkable high fidelity experience.
For example: Lets say you have a great headphone amp combined with some high end headphones. The headphone amp only has one headphone port. Now you have three choices; You could split the signal from the headphone port, split the signal from the source before the headphone amp, or plug the headphones into the SubPac's headphone port.
The SubPac passes audio through to the headphones without adding or subtracting signal. It does not act as an amplifier. Keep this in mind when placing it in the signal chain. It also accepts line level, not speaker level so refrain from connecting it to a port that would normally receive a speaker. This will prevent it from getting direct current.
Surround sound connections are also possible depending on your setup. Find the LFE or Sub line output from your receiver and connect the SubPac. It can also be effective using the mixed output from the headphone out if that is present. The last scenario would be to split the LFE amplified signal before the speaker with a switch and then placing a high to low adapter (speaker to line level) before ending at the SubPac.
The SubPac is matched for headphone impedances 32ohms and under, which pairs it with the wide majority of headphones on the market. For higher impedance headphone users the best practice is to split the source signal to the SubPac and use a dedicated headphone amp.