[matthew]

I suppose that since I found the primes a close match to the 24-105, I'm wondering, "will I gain much?"
In order to buy the 24-70, I think I need to sell all 3 primes......

Well, going back to the OP, the issue is that the quality of the 24-105 is close enough to better, but too slow, hence the 24-70. But with that switch, you're still losing more than a stop @50mm and @85mm, as well as losing your telephoto. I've heard great things about the 24-70, but most of them aren't about how small and light it is.So you're giving up small size, speed, and reach. You're gaining image quality (probably, but what do I know?) and flexibility. Presumably going to one lens will also cut down on the sensor cleaning.

(Oh, and you're leaping forward about 40 years' worth of technology -- from the 50's to the 90's. )

But in addition to the financial hit of switching, it's coming across that you simply like primes. (Maybe you have a well-hidden contrarian streak?) Personally I'm not a fan of standard zooms, even though I have a couple of them, so I can certainly appreciate sticking with a system you like.

And say Hi to NN for me.