When set up as a 5.1 system, there is no delay.  A 5.1 system is a single room. The only delay in TV sources is when you group two separate rooms together. 

Sonos has some specific terms to be aware of, but your system, when ‘bonded’ together, should make a 5.1 system. All those speakers become a single ‘room’ in the Sonos software. 

The Sonos Arc is your front three channels, the Sonos Amp would power the two surround speakers.

The ‘delay’ you’ve read about is only when grouping that ‘room’ with another Sonos ‘room’ when playing the TV. There is no delay when streaming music, and never within that single room. I usually encourage people, once they’ve set up the system, to go into the surround settings, and switch those rear speakers to be ‘full’ rather than ‘ambient’ for music play back. That way those rear speakers act as normal stereo speakers, rather than just support speakers for the Arc. 

Edit….I had a lot more typing to do than @jgatie, but we agree ;)

Thanks folks!