20k and halfway through the tires? That's pretty decent, looking at about a 40K mile lifespan and right in line with the Pirelli rating. Not sure what you were expecting.
Assuming V6 on 17's or 18's, as far as brand any of the majors would do fine.
Yokohama
Kumho
michelin
hankook
bridgestone
continental
toyo
goodyear
pirelli
People have their preferences, and everyone has had good and bad experiences with different brands. The only ones I'm really uneasy about are made in china tires, everything else seems pretty decent.
Just find something with a decent treadwear equivalent to what you have now (about 400) at a price you want to pay. Some places (like discount tire) will match tirerack or amazon prices, so make sure to look up the model you decide to price compare. Also check discounttireonline.com. Same company, but operates on a different arm and sometimes has better(though sometimes higher) prices