Choosing Sybase, Oracle, or Informix?

I am a graphics application programmer writing a GUI and imaging front end for financial analytics packages. Am using C/Motif/Xlib on a Sun Sparc10 (SunOS 4.1.3). We want to put a database on this machine: either Sybase or Informix or Oracle. I'm not sure which one to choose. My expertise is NOT in db management, so I would want something with not too steep a learning curve. Data stored would be simple tables with anywhere from 100k to 500k records with 20 fields per record containing mostly floating point (double) values but also some integer and character. Concurrent access will be limited to 5 or 6 users on an NFS network of sparc's and PC's (this is NOT a big shop). Requirements are quick retrieval (updating is secondary) based on asking for all records from a given table with one or more fields matching corresponding range values. Any comments, ideas, and input would be greatly appreciated!. Rich Parker Hotchkis & Wiley Los Angeles, CA hotch@netcom.com