I have all upgrades through and including 5th level. Many of these are of the type for every group of level X gens, base income for level Y goes up by some amount. After these, I've noticed that buying certain level crunchers, and then buying back as many generators as I can, that this actually LOWERS over-all pixels/sec!
I feel like I have to review all prestige awards and doing a calculations, before I buy a given level cruncher. Seems like a lot of work. Could you publish the calculations in the game?
Also, the ingame instructions are not actually instructions, per se. I spent a lot of time playing before I realized what challenges, prestige awards, crunchers and even the 1x, 5x and 25x buttons all did.