Do I need a preamp/processor?

Hi everyone, 

Home theater is new to me so I need assistance. The question I have is do I need a HT preamp/processor to properly listen to movies (DVD, streaming etc)?  I currently have a 2 channel system using a Red Dragon S500 amplifier, Schiit SYS preamp, and Kef ls50 speakers.  I’m mainly streaming Tidal through a Sonos Connect which is connected to the preamp via rca.

 I would like to add in the capability to listen to movies through the ls50s and Red Dragon. I’m currently doing it by running a toslink cable to an external DAC then rca to the preamplifier, then rca to the amp. The hook up works but it doesn’t sound that great. 

I was planning on upgrading my preamp anyway, and it was suggested that a HT preamp/processor might be a good alternative. It sounds very appealing since it would do double duty for me. However I’m still vacillating between the two choices since some nice 2 channel preamps pop up every so often.  

Please help!