There is no (reasonable) subway/train connection between PRG and the city center that doesn't involve a bus or car.

There is a public bus that goes from the airport to the main train station. From the main train station, if you know the direction and have light, wheeled luggage, then it takes about ten minutes to walk to this Radisson hotel. A word of warning about the public bus: sometimes the bus is so packed that it's hard to find a place for luggage even if with only cabin bag-sized luggage.

The airport car transfer I booked online cost between 500-600 Czech for one-way service (in either direction) between the airport and the hotel. I recommend that over public taxis at PRG airport or from the city center. The hotel's own recommended car service is about 50-100 Czech crowns more than what I used when at the Radisson Blu Alcorn several weeks ago -- a pretty good deal still, considering the rip-off taxi problem in Prague.