Greg tech seems to be a very good addon. I rather like the ability to customize the systems more (with the adjustable energy storage, the quantum chests are very helpful, etc.
About the fusion reactor:
I really like the design with something in the middle and coils around it, though technically it should have torroidial symmetry rather than spherical (magnetic fields are torroidally symmetric). Is there any way you can change the tritium production method to involved neutron bombardment of lithium? Both the fusion and fission reactor would produce large amounts if neutron radiation, which could then be used to breed tritium (see the last paragraph under "Reactor Overview" http://en.wikipedia.org/wiki/ITER )
The super condensers look perfect for powering a large railgun or laser system, there the former could be used for moving things, and the latter for either a different type of fusion (just for generating materials, not power production) or as mass excavation tool (enough energy into a FEL and you should be able to evaporate some mountains).