Any 2.5" dual system with straight thru performance mufflers will give you good performance. I have a $150 non mandrel bent, muffler shop special with a $100 pair of used ultraflows on my car and there is no difference in performance between the open dump or running thru the pipes into the mid 11's.
If you need stainless because of the climate you live in, get stainless mufflers, too, because the will rust first. Avoid flowmasters and "turbo" style mufflers because these have more backpressure than the straight thru designs. They may sound good, but will cost performance.