davian thule will be a dreadnought when you complete all missions with prime gene samples
What he said.
Also, I recommend doing the gene sample missions first. Thule is EXTREMELY powerful, whereas the Astronomicon only gives you the Oribtal Strike and Drop Pod.
Doing Meridian first may sound good because it will allow you to get Terminator armor, but I don't recommend it, as it will give you three planets to have to defend, rather than just two if you stay away tell everthing else is done.