I have had a car where the bolts were so rusty it was incredible, I cut a small opening on each side of the center of the car with the back seat removed to get the bolts out because I had to pound them out the whole way. My other car (no winters) they came out no problem. If they are rusted into the sleeves of the bushings you could be in for a real battle. In that case sockets and breaker bars will not do it.
There was a guy on here who had the sleeve in a bushing spin rather than have the bolt break loose, search for that thread, he had a nightmare. You won't know until you try it.
Since you have new arms, cutting the old ones off would let you get the axle out of the way to hack the stubs out. this is the worst case scenario.
How rusty is your car?