Informix vs Illustra

Hi folks, I am new to the database world, well, experienced in the .dbf environment (dbase, foxpro...) but new to the REAL database world.... We currently need a database for 2 tasks : - build an accounting system for an Internet access provider It will be a fairly simple accounting system with full featured statistics. It should support about 100/500 request per minute since any connexion will be authentificated and logged bu the database system (using RADIUS for those who are familiar). - use as the core database system for designing web server who need to access on line a mass of data. Typicall application would be a YAHOO type of directory, or a virtual museum with many paintings, pictures and sounds. The server will be an SGI Challenge, with one processor. We have reviewed the current databases on the market, and we are in favor of Informix or Illustra. Can anyone here advice us on the choice between these two engines, knowing that they will merge in a year from now. Thanks for your help, jerome.