Ak-sys make digital i/o obsolete

this is just my personal opion, but my mixes come out better in the mpc4k
than when i mix on pro-tools for some reason or another when i bounce a pro tools session to a stereo mix it sounds really thin so what i been doing lately is doing everything in the mpc4k resample it to a stereo wave i use aksys to drag the wave into a pro tools session to record vocals after that i drag the vocals back into the mpc to continue my mix it sounds alot cleaner
than when i was doing everything in pro tools now i find myself with know use for digital i/o

What your hearing with the PT is the 'stereo' buss limitation. The processing it takes to slam (digitally) multiple tracks together to send to the stereo buss is pretty intensive as well as limiting. Try taking multiple outs of a PT rig and sending them to a hardware mixer and "summing" them there. It's night and day. Much more headroom even in a cheaper console.
-turn