A "transport" is just the spinner in a CD player. Almost every CD player has a coax digital out so can be used as just a "Transport". Your Audiolab has no DAC in it so you call it a transport rather than a CD player. Any player including universal players like an Oppo can be used via its coax out to the flex and into a digital amp. However, you cannot play an SACD into the flex.....nor is SACD info allowed out of a normal coax out. The amp and the Flex are PCM only devices. You could make an integrated amp with digital amp modules where you change DSD info to PCM before it goes into the main pcm to pwm conversion.....Technics does this. You can burn your SACDs to a computer and use software in a computer to change it to high speed PCM and then output that to a streamer like the IFI Zenstream to play through digital amps.
You get a Flex and a single stereo digital amp and you have a blast....you add a second amp and get rid of the crossover in your speaker and you are in heaven. No more bass nodes.....full equalization......no more binding posts....no more passive xovers.....just pure sound.....dynamic as hell. Fun times await folks......the future is now!