About any British Breed will do well in Pa.
Angus, Red Angus Polled Hereford, Hereford, Shorthorn, Murray Greys. Don't know much about British Whites but they should do well too. Campground Cattle, will probaly elaborate more on the British Whites as he is probaly the only one on this board that knows very much about them.
Aaron, go to your local stockyard and see what's selling best. Then choose.
Assuming you will be rather small at the start you will market most of your cattle through a stockyard I would assume. See what the buyers are paying the most for and then look for cattle that will produce what those buyers are buying.
Don't go just one time, go at least two times or more (just in case there wasn't a full selection). Spot a buyer and ask! But not when they are buying/bidding but during a break or change in auctioneers. Although I sell privately I go to the yards every once in a while and chat with the guys on the back rail (that's where our major buyers hang) and see what trends are happening and any other gossip.