Just have to chime in on this one being a manager at a tire/auto shop. The stockers IE the BRS potenza re050s are excellent tires sticky as hell, no road noise, great sidewalls for cornering. HOWEVER the 140 treadwear rating SUCKS i have just over 12k on my 07 ms6 and mine are spanked. Even with excellent roation habits and weekly pressurechecks.
Now for the set i suggest to anyone looking for the same attributes as the potenza without the terrible wear rating, would be the nitto neo-gens. I put a set on jaxjeff's 06 ms6 and he loves them. 10k on them and they still look like new. and they are resonably priced at about 105$ a pop.