im looking at removing the middle silencers and cats from my otherwise standard n/a. My question is, what will this sound like with standard rear boxes? Has anyone used this setup? And if so what sort of noise did it produce? Thanks.

IMO you will need to retain a (small) expansion box up the front end of the system on an NA. Otherwise you may lose power at lower revs. The expansion chamber creates a low pressure area to assist more efficient gas extraction at low engine revs. Doesnt apply to turbo cars as the turbo forces gases down the pipe.

The noise etc is manly determined by the silencer at the rear as expansion boxes dont normally contain any packing material.