Is a Sub required for HT

No....but!

Your receiver's bass management will route all the bass to existing speakers.  The experience of watching a movie with a well i tegrated sub is transformative.  Especially naval movies, but integrating a sub well is a ton of work to do rignt.  if you cant take that effort, leave it out.

To do subs well usually requires bass traps and DSP in that order.

I already have GIK room treatment, including bass traps. I don't understand why you say integration for HT is difficult? I won't be using a sub in my 2-channel system.

I don't understand why you say integration for HT is difficult? I won't be using a sub in my 2-channel system.

It's really not hard to add a sub to home theater.  2 channel yes, but HT is a walk in the park.

I agree that the sub will make a movie that has that LFE channel a whole different experience.

Looking at the manual for your Marantz receiver, the default setting for Subwoofer is "yes". If this has not been changed, you are losing the LFE channel. Make sure it is set to "no", then it should send the LFE signal to the main speakers. This can make a difference in overall performance. Take a look at page 196 in your manual.

Hi Ric,

This is an easy one. Continue to build up your combo 2-channel/HT system. Get the rear speakers installed, go through the setup routine in your receiver and try it out with some of the types of movies you enjoy. If you find that you would like LFE (Low Frequency Effects), or you need some additional bass in your HT system, add the sub and re-do the setup routine.

For me, if I was going to go through the trouble and expense of adding HT to my 2-channel listening room, I would definitely want a sub to add the final dimension of sound to the HT experience.

As you know, the sub will have no effect on your combo system when listening to 2-channel music, so it's simply a matter of "do you want/need LFE or additional bass when listening to HT sources?". Your choice.