Should I use tomcat or a application server?

I'm gonna start to develop a web application which will be accessed by 20-30 users simultaneously. I'll use a 2gb(ram) server and tomcat for a low memory comsumption. Can Tomcat solve my problem without the Java EE implementions and provide a good perfomance application? I don't want to use JPA, CDI and the other stuffs becaouse of my little memory.