@george_r
You can use any preamp with a home theater system. The bypass is just so you don't have to set the volume from the preamp- its controlled by the remote of the home theater.
I have an NAD purifi based amplifier, and a previous A/B amp from NAD which the C298 replaced. Class D has arrived and outside a straight-up Class A amplifier, I will not be going back to an amplifier that produces unwanted heat. I am not here to tout any manufacturer, only to share experiences to help others as this site has assisted me over the years to understand how to get better sound without spending a fortune.
If you have constructed shelving underneath your floor, you surely do have space issues. But an amplifier- any electronic device- which is placed outside a controlled environment will be subject to temperature fluctuations, moisture, dust, and vibrations which all pose significant risks to the sensitive electronics within an amplifier. Assume you have a trap door? Got photos? Your cable runs must be lengthy!
Not sure what you were trying to gauge or accomplish with your first post that invoked my handle, but I was trying to help. If you were not looking for help with your rig, what was your intention?