Java Standart Edition 6 vs symbian
This is more of a developer question than a consumer question. You may try the Java discussion boards on Forum Nokia. If you do post there, you may want to include the specific functionality of J2SE that you are missing in J2ME so that more experienced developers can suggest alternatives.
Lumia 920, Lumia 800
Nokia N8-00 (NAM, Product Code: 059C8T6), Symbian Belle, Type RM-596, 111.030.0609
Nokia 5800 XpressMusic (NAM, Product Code: 0577454) Software v51.2.007, Type RM-428