1. For now, surplus 5.45 x 39 for the AK-74 is as cheap a rifle round as anything these days. A lot of people buy 5.45 uppers for their ARs for practice. Hell, the price of regular-old AK-74 mags over 5.56 AK mags should just about seal that.
3. AK are heavier than Colt 6920s, as far as I know, though your 6920s are "fully equipped", but then you'd need to "fully equip" the AK with sling, light, optic as well for it to be equal. At which point the AK would then be heavier again, and you just kitted-out an AK to run with in lieu of a Colt 6920, which might be worth a slap in the forehead.
Alternately you could get a lightweight barreled carbine upper with Daniel Lite quad rail for that Colt? Just thinking out loud.
4. AK's a better trunk gun than a nice equipped Colt, for sure.
5. AKs are easy to work on, but they're not modular in any sense like the AR, so there's a LOT of cutting and filing if you want to do a lot of stuff to them.
6. Philosophically, and this is just my feeling on the matter, once you start really spending coin on an AK, why not just get something more modern and sophisticated? Unless you just want a tricked-out AK, which that's all good, too.
7. Yeah. That's why I'm thinking 5.45.
8. Don't know that one.
9. I think you're kind of in a weird logic hole here, because you seem to be wanting to really kit-out an AK (and it'll cost a lot, especially "Krebs-ing it"). Like, you're wanting something modern and sophisticated from an AK, like your Colt, which the AK is not.
10. Okay, here goes. Here's what I think you might be wanting to turn your AKs into:https://www.budsgunshop.com/catalog/pro ... s_id/60741
They're great, they're an AK style piston gun with mostly AR controls, most of the skills wil transfer right over from your ARs. They take all your AR mags and shoot 556. The initial price will be less than a high-end AK. Hell, you can even bolt all your AR accessories to it for the most part. It's more accurate, modern, and modular than the AK, but still a hell of a lot less modular than the AR is.
Of course, like the AK, it's also heavier than an AR.
Hope that helps.