Fritz 13 - download, no waiting for shipping! Available from Amazon Digital Services, Inc. Download size is 3.3 GB and should take 45 minutes - 5 hours on broadband. Database contains over 1.5 million games, over 10 hours of video instruction. Fritz is, in my opinion, the best GUI available because it is the easiest to use. I recommend using the top-rated Stockfish 5 engine which is available for free download from the Stockfish site.
Chess King 3 2013 version with Houdini 3. 5 million game GigaKing Database, free updates 2013 classical and random playing modes, supports up to 6 cores and 4 GB of hash, 1500 puzzles. The Houdini 3 engine is worth the price $29 alone!
NOTE: When evaluating positions it’s always a good idea to get the opinion of at least TWO engines. The two I recommend are: Houdini because it gives the most realistic evaluation and is strong in the ending even without the use of tablebases. Stockfish is currently the top-rated engine and is very good in middlegame planning and tactics, but it is not as strong as Houdini in the endings. One word of caution: it’s evaluations usually are considerably higher than other engines.
Critter 1.6 - Another excellent free engine for double checking evaluations is Critter which is available for download from the Critter site. Critter's evaluations are closer to Houdini and it's only slightly weaker than Stockfish and Houdini. The SSDF complete engine rating list is probably the most accurate because of its slower time controls (40 moves in 40 minutes vs. the 40 moves in 4 minutes) and the standings there are:
1-Stockfish 5, 4 CPUs (3286)
2-Houdini 3 4 CPUs (3264)
5-Critter 4CPUs (3175)