ChessMagician you need to know if you have a single core or multicore processor. The Deep versions require multicore processors to deliver their full potential. If you do have multicore then the Deep version will work and be stronger for sure but only you can decide if it's worth the extra $40. Go to this link and check out the Independant Testing results http://rybkachess.com/
Here is a link comparing Rybka3 and Deep Rybka3 http://rybkaforum.net/cgi-bin/rybkaforum/topic_show.pl?tid=8396
Oh yes... the difference is in playing strength a part of which is how fast (deep) the engine search during its analysis. The computer definately has alot to do with it. The interface you use... well the Chessbase version of Rybka uses the same interface as Fritz 11. The are identical. I have not used Aqaurium but if you go to http://rybkaforum.net/cgi-bin/rybkaforum/forum_show.pl you will see a forum for Aquarium discussion. You can also download the demo version
A couple of quick questions about chess analysis software. Would you recommend using Deep Rybka 3 or simply Rybka 3 given that the former is about $40 more expensive. I intend to seriously advance my chess level, but at present I am not much higher than a 1600. Is the difference only running speed, and if so does this depend heavily on the computer?
One other thing, which is the best program to run with Rybka - Chessbase, Fritz 11, Aquarium or some other?