While I'm sure some companies are better than others, I've had limited success having leaf springs re-arched. The ones I have used did not last as long as the originals. I've had very good luck using new leaf springs from Inland Truck Parts, although I will admit I've used their products only on trucks, not cars. My last product that I used from them were replacement leaf springs for a Chevy diesel pickup and the owner was very satisfied.
A quick search on their site says they do re-arching also. (Search engine the company)