I don't think you'll see much, if any, tonal change between having the ubend in there and not having it in there. The ubend may free up 2-3 horsepower, which is nothing all that measurable.
Your choice of muffler and resonator (or no resonator) will have a far bigger impact on the sound.
HeavySS: A ubend is a peice in the 00+ Impala exhaust systems where an O2 sensor is plugged in. It follows the catalytic converter and checks the efficiency. It is literally a bend in the pipe that looks like a U. It's a bit restrictive. Removing it means installing an aftermarket downpipe from ZZP or another company, or simply cutting out that section of pipe and replacing it with a straight section.
Removing the Ubend may cause a check engine light due to funny readings from that second 02 sensor. In 2000-2003 models, an O2 simulator can be used so that you don't need to drill a hole in your exhaust and reinstall that sensor... but you may fail emissions if they look under the car and realise you no longer have a second O2 sensor under there.