I have thought of getting a QB78. I have a 160 first model that has almost no power. I had thought of getting a QB 78 and moding it to = my Crosman 2100 with out the pumping. I know Archer sells a lot of upgrades. I would probably get them to install.
sacked spring and a distorted poppet seal.
Drop Archers upgrades into a 78 and see if that's enough for you,there's more if you want it,though you'll need to set up for bulk to get the most out of the gun.
Do some searches here on QB tune, light striker, pillar valve.