We stayed at this hotel by accident because our original hotel I booked, the EuroAgentur Crystal Palace overbooked us and sent us here. It wasn't a big deal they ordered a cab which they paid for and we were in the K K Fenix 15 minutes after we walked in the Crystal Palace. We were very pleased with the K K Fenix. It has a very nice lobby, very friendly staff who all speak English. The room was great although the double was two twins pushed together. The beds were very comfortable as was the comforter. Room was spotlessly clean and spacious. Bathroom was a good nice and the shower was clean with plenty of hot water and decent pressure. The TV had 7 english channels including 3 HBO's. A minibar was also in the room to use or store your own drinks in. The room safe worked great. Breakfast was superb and open until 12 noon on the weekends, they were even letting people in ten minutes past 12. Champagne and O.J. was available for mimosas which was a nice touch.
As for the area, it is next door to two cabarnet/strip clubs which don't pose any problem although the first night it was very loud down there due to a Stag party, but we had ear plugs so it wasn't too bad. The metro stop is a three minute walk, and a mini market with alcohol is directly across the street from the hotel. Wenceslas Square is not even a one minute walk away, but that didn't matter to us. This square is expensive to eat and drink in, filled with seedy people and a haven for the most annoying, offensive, drunkest and most obnoxious group Europe has to offer which is the British Stag Do. I'm from the States, but am currently living in England temporarily, but if you're not familiar with a stag do is, let me fill you in. Its basically an overblown bachelor party where a group of British guys usually packs of 6-15 of them go to a cheap place in mainland Europe for the weekend wearing all matching shirts saying "Tom's Prague '08 Stag" or something similar or they were fancy dress in which they all dress up in costumes. They travel in packs are very loud and disrespectful and are drunker beyond belief the entire time. They prefer to hang out in either British pubs or Irish pubs. They are very, very loud and obnoxious and if you want to enjoy the culture of Prague, you might as well visit another area such as the Old Town north of Wenceslas Square or the Mala Strana area near the Castle, which is on the left bank of the river. Its quieter there with cheaper food and drinks.
That said, the hotel is very nice and we had a great stay , my negative comments were based on the area the hotel sits in and the type of people you may come across there. If you're looking for a quieter area, avoid Wenceslas Square which this nice hotel is basically in.