Greetings, Well the best and most useful tech tree I've found Online was at the Kuat Drive Yards.
http://se4kdy.cyberwars.com/
On the center frame click "mods & files" and the first selection on the screen that comes up is a well organized tech tree where you can actually see what leads to what with relative ease. It prints out at 15 pages long but it even covers all the racial tech. My compliments to the Drive Yards for supplying such a useful tool to the community and I'm sure it will help answer those tech questions.
Duke Fred