A good exhaust system will usually sound better than a muffler delete, especially on the V6. I've heard muffler deletes on the LFX and the LLT and even Flowmasters and other lower priced axle-back systems sound better.
But it will not void your warranty for anything other than the exhaust. If you want louder exhaust on a budget, get axle-back by Flowmaster or Magnaflow. If you want the best sound, a full cat back system with x-pipe, resonator delete, and MRT v1 or v2 typically get the best sound out of the V6.
Check out
the LFX engine/exhaust forum for more information.