yah mon if u have 2 get crushed its no big deal. mabey u might get 2 more hp out of mandrel bent[ i belive that takes a special type of machine].
crushed is fine, just go to a reputable shop and make sure they do it right, just tell them u want the best flow u can get and i dont even giva damn i will stand in the bay while they do the work just be cool and talk to them and tell them u want good flow and they will do a good job and yes if u have the money get a hi-flow cat while ur at it if they have one even for a decent price.
yes get 2.25" thats good for a decent turbo setup and n/a as well, and yes get a hi-flow muffler either a straight-thru design or if you want to look stock like a sleeper then u can go w/ dynomax or some of the magnaflows, they sound good after your car is warm and have good flow.
when ur car is cold they can sound raspy cause of the type of insulation they have, i forget what its called.
but yeah just go with custom bent 2.25 cat-back ull be fine. but b sure 2 upgrade your cat to a hi-flow sometime soon to complete your exhaust. and then either header or turbo header depending on what your have planned for your setup.