Just to throw a thing out there:
I also think EXU is balanced by itself, even if he converted it to EU the modder did think of generally gamebalance.
And as you said the x8 & x64 are like compact solars. If we go with adv solars yeah they break the gamebalance because (if we go for classic) they require 64 Uran and about 900 uum and automating the progress of production is easy.
Now if we go to compact solars that is not really breaking the balance (even the 512 eu solar pannel),
because you have to think about that. The balance is based on what you gain, it is the balance of what you gain from the cost (stupid explained) but a 512EU solar pannel are simply (+little extra cost) 512 solar pannels and they are freaking expensive even with exp!
Same goes for all compact mods.
Now to Extra utils x generators...
They are balanced for each induviual. I do not even thinking about using RF as mainPower, but these generators are really balanced and that is a thing, they produce RF but i do not use RF i strictly convert it to MJ (1.6.4 versions do not matter here), and even if you have a x64 generator and use it,
there are other problems that you have to solve, where to go with the power, i mean a netherstar generator which produces silly amounts of power is hard to handle because of transfering and storing it,
that to handle will almost impossible if you are using x8 and it will be impossible if you are using the x64 ^^" The cost of that generator is imens so i think when you have a netherstar generator you have a use for it... Unless you are Soyran xD
I hope you get my point.