Whatever you do, DON'T go with selling your GPU only. 400 USD is laughable offer for a 2080 that is on par with the 3070 in performance. I mean that would translate to you selling something that's kinda like the 3070, but with tried and tested compatibility, possibly better thermals and lower power usage for 400 USD. Because of this, having a 2080 might be the better deal if it's cheaper than a 3070 FE in my opinion when you have a Dan-A4, because it's more compatible. Your 2080 is ALL GOOD. 120 fps in Warzone, you're good to go for years. And also if you're without a gpu you still can't use the computer, it's the same as selling it alltogether.
So either sell it completely or better yet, keep it (especially if you're fond of it) and just use it, that build is the current TOP tier for christ sakes. You're set! Just recently built your rig I presume, take time to enjoy it. Also, my main reason for anyone with a 2070 or 2080 to not upgrade is that you can't even justify the difference in perofmance with the current games. Warzone as you said, will run above 100 fps with both gen, so why buy anything now that will only matter much later? The games where you could acutally see what difference the ampere cards make are not here yet, they're yet to come, right now these gpu's don't matter and just degrade with time. The games when they will become relevant with will only arrive later and by then, maybe these 3000 cards will be cheaper.
So just lay back and let the consumer fanatics ahead, give it time for the amprere-craze to wear down and when the purple dust settled and the competition (big navi) arrived, we'll see how things are. Who knows, maybe we will find a more DAN-A4 friendly ampere card by then. OR: with a 2080 you can also skip the whole ampere line alltoghether and wait for the upcoming gen. I don't see the reason to upgrade gpu or cpu for just a single gen anyway. There's literally no point. So my vote: KEEP IT.
