How to merge my 2 Channel and HT Systems?

It can be done, the biggest problem is what is between the two channel speakers. If your screen is wall mounted you're in business. Once I went to a FP and placed the screen on the wall, getting rid of the obstruction between my L/R speakers, a whole new world opened up.

No matter how well you approach it, optimal L/R speaker placement is different for HT and 2 channel. So a combined system will have compromises. But once the L/R speakers have room to breathe the compromise is modest.

I have an 2 channel set up (cd player -> dac -> preamp -> 2 channel amp driving left and right; sub takes low freq thoght he preamp sub out) that is "connected" by HT bypass to a NAD multichannel reciever (does all video processing and multichannel audio and drive center and rear speakers). So, when listening to 2 channel, no compromise as nothing runs through the HT setup. With HT, the amp is contoled by the volume control on NAD (through HT bypass)

Does your Anthem has 7.1 output? If it does, I would connect the LF and RF to one of the input on your Plininus. This way, you can use the Plinius in both 2ch and HT. If the Anthem does NOT have the 7.1 output, I would connect the 7.1 LF and RF outputs from your DVD/Bluray player to the Plininus. Same concepts.

QN

I do it as follows:

Surround processor to the "unity gain" input on stereo preamp. The sub is on the LFE output from the processor. I run two channel as full signal with no subs. For HT, I hit one button on the preamp remote to change from the two channel input port to the "unity gain" port.

Wyred 4 Sound sells a stereo preamp with an even easier HT bypass that lets you run the subs in both modes. I only changed from it because the BAT preamp sounded better in two channel.

Moto Man

I have done this for years. I have the stereo outs from the processor go into a tube preamp. The tube preamp has two sets of outputs, one connected to the multichannel amp and one connected to tube mono blocks. The preamp is set to unity gain when listening to surround sound. When I listen to stereo you do have to switch speaker cables from the surround sound amp to the tube mono blocks and make sure the surround sound amp is turned off as my speakers do not have two sets of connectors. To some people this may be a pain in the rear but works for me.

I really do not have another choice as the room is too small to have two separate setups.