Well if you want to use your stock tips on a new exhaust, somehow they will need to come off the stock exhaust... no? :-)
We also have round tips from Magnaflow that can be put onto your cutom axleback exhaust. Many people also opt for no tips at all to keep the 5.0 happy and the honda boys cornfused. Just a plain black 2 1/2" pair of tips. Looks stocker than stock and is more popular in So Cal.
For $100 cash and carry or $140 installed we can modify the stock muffler internally to flow more. There is a cross tube that can be surgically removed to open things up a bunch. It affects the sound very little.
Then again we can build all the same options that we make for the EVO X. In the end (I think you are local?) you design it and we'll build it your way.