Look at the equipment first. If they use seat cutters rather than stones, ask how many angles they use. If they use stones, move on. Most performance shops are using at least 5 angles on thier cutters now and the high end equipment can cut a seat that is within .0001" of perfectly round and requires no lapping in. Expect to pay for quality work. Also, an easy way to get the best results is to replace the valves as those look rather haggard and stock.