buy an older version, that would be cheaper
Fritz vs. Chessbase

Fritz is the playing program. Chessbase is a database system for chess. Chessbase includes Fritz I believe.
If you are only in for playing, Fritz can do it all. Chessmaster is also good.
I recommend Fritz.

I'm not sure of your purposes so I'm not sure how much you need a database program. Fritz does come with some database capabilities.
In the meantime you can always download a free version of Rybka 2 and a free interface (like Arena) and see how you feel about what they offer.

It might be an idea to become a premium member, you get TT Chess mentor and videos, as well as a large database.

I would get Fritz 12, the new one. It is about $55 American I know. It has a lot of useful features. Can analyze your games, you can save them in database folders, you can open all your PGN game files with it.
Chessbase is a few hundred dollars for the smaller version, and almost $400 for the full version. I have it and I love it...but, I don't use it as much as I expected. If you get Fritz, you can learn all the features and decide if you need more from there.
http://www.chessbase.com/shop/index.asp?cat=ChessBase&user=&coin=

Depending on how much guidance you need, using a database to discover and learn about openings and variations may be all you need. I use Powebook in Chessbase and it spits out won/loss percentages move by move--useful for picking out variations and what-if-ing possibilities that occur to you. With a little work investigating openings in a database can inform you too.
Openings for players less than, say, 1600 are not so important. Just knowing what you know and learning from experience is good enough. If you really wanted software for your openings though I say go for it. Enjoy chess the way you want. It's not your profession.
If you want an engine to spar with and not crush you, you'll have to ask around. I know Chessmaster has a huge variety of opponent strengths and I think Fritz does too. You'll have to research a bit to see if others have found them realistic opponents at that level as some play well, make a horrible move, then play well again, as opposed to essentially a series of good but not super-precise moves.
When I want a competitive long game I have an old handheld that I can only win 40% or so against. It doesn't throw away material and I have to do some outsmarting to score on it. It seems like a real and reasonable opponent most of the time.
Again, ask around and see what others think about their silicon opponents.
difference between fritz and chessbase?