AMD FX-8320 bottleneck CF Rx 480's?

YES

That processor would bottleneck a single RX 480. FX Series
processors are very outdated and weak...

It's a good idea to understand what exactly a bottleneck is.

Your CPU will be able to deliver a certain amount of frames in a game, regardless of what video card you have. Let's say you're playing Battlefield, and your CPU can deliver 50fps, and a single RX480 at max settings only gets 40fps. Your CPU in this case is not bottlenecking your RX480. However, you can lower your graphical settings to the point that your GPU can deliver 60fps, but you'll still only get 50fps as that's all your CPU can deliver, and without changing your CPU or GPU you now have a CPU bottleneck. Be aware that one will always bottleneck the other, or your framerate would be infinitely high.

For what it's worth, the GTX 1070 is close to twice as fast as an RX480, less than twice as expensive, and only draws as much power as a single RX 480. Crossfire doesn't work in all games, and in those that it does, nowhere close to all of them scale perfectly. I wouldn't bother with Crossfire, just buy a single faster card.

For a from-scratch build, the common recommendations are an i3 6100, i5 6500, i5 6600K, i7 6700 and i7 6700K, depending on your budget and uses.

Give info about your mobo. The fx 8xxx series are still doing fine, dont worry a decent OC(up to 4.7-5.0ghz) will go perfect with those rx 480s in Crossfire.
This is vid showing the performance you can get from your pc: https://www.youtube.com/watch?v=iGgCk40S5uw
The guy used a fx 9590(which is basically a Overclocked fx 8350/8320, and a pair of r9 390x(About the same perf as two rx 480s)

Get a closed loop h100i and you should be good to OC that cpu

No it is not worth investing anymore money on the FX Series. They are very
outdated and weak no matter what overclock you have

Whats your budget exactly for a new CPU and Motherboard?

If you already have the FX, I'd say grab a single 1070 instead of CF 480's. If you don't have the FX yet, buy something else.

EDIT: An FX-83xx would be a decent upgrade over what you have. I still recommend against Crossfire though. When you're ready for more GPU power, sell the card you have and buy a new one.

They'll work together. CPU and GPU bottlenecking is a complex topic. Buying a faster card will never lower your framerates, but neither will it improve the maximum framerates you can already get by lowering your graphics settings with your current card. Mostly, GPU upgrades are good for allowing you to turn up graphical settings in-game, and not so much for allowing higher framerates - that's the CPU's job.

Am i missing something? The FX series are very outdated and you should not sink money into them

The GTX 1070 will still be bottlenecked a huge amount to where the GTX 1070 is just a waste.
The processor is very weak and will hold your GTX 1070 back

@Mac070:
Being only a few years old, the FX series is not "VERY OUTDATED" as you claim... however the Athlon FX series is, something like 10 years old, but who in their right mind would bother posting about upgrading to decade old tech now? As i can see from your repeated blanket statement about AMD, you're clearly an Intel fanboy, and don't recognize such things as budget building "bang for your buck" builds.

@PolrYT:
The only thing you'll notice a significant performance increase from even within AMD builds, is upgrading to the PCIe 3.0, APU's support PCIe 3.0, and though they aren't "more cores" they are still quad cores, with the compute cores from the GPU side of the APU they can act in upwards of 12 cores, some tinkering required. I use my personal experience of an ASUS Crosshair V Formula Z AM3+ using an FX-8320 oc'd to 4.0Ghz with 16GB DDR3-2133 with UEFI boot and GPT partitioned OS drive, for as much of a performance gain as i can get, and it still is outperformed on Battlefield 1 by the APU build regardless of the GPU used...

My roommate had me build him a new rig, he went the DIY route instead of using ibuypower again after they installed his liquid cooler in such a manner that it kinked the tubes and the water block had a bulge and corrosion on it... but that was Intel, a first gen i5... he chose to go AMD...

He was super excited when everything came in and i put it together for him, he had played BF1 on the old setup a few times, and immediately noticed a massive performance gain over his i5 and a 770 using the new XFX RX 480 and an A10-7890K APU on an ASUS Crossblade Ranger the reason his build was doing far better than mine regardless of what GPU was in use is primarily due to the PCIe 3.0 on the APU board, and the PCIe 2.0 on the AM3 board... i couldn't believe it, but that is the only thing that stands out between the two, he has four cores, i've got eight, he's at 3.5ghz, i'm oc'd to 4.0ghz, same capacity of RAM, just he's using DDR3-1600 and i'm running DDR3-2133.

CONSTANTLY, i belly ache how my laptop is faster than my pc... the laptop has an A10 elite quad core and 6GB ram, and it often performs far better than my PC, why? possibly due to the fact that i have bad luck mostly, but more due to the fact the APU's are newer and sport the fancy new bandwidths of the PCIe bus. I've tried OC'ing my PCIe bus, but it always crashes out over 110mhz and i hear that PCIe3.0 has something like 200Mhz which is a significant data throughput advantage.

the CPU bottlenecks? probably not, but the board does for sure! Definitely looking forward to the new AM4's! would LOVE it if they go up to PCIe 4.0 OMG Crossfire might be worth something then!

Oh and that's another thing...
pretty much, if you can, stick with ONE card, if you absolutely have to get two cards, be readily prepared for games to not support it and lose performance rather than gain it... resource: personal experience and HERE

AMD says: "PCIe® x16, 3.0 for optimal performance"
what they don't say is it's not supported by AM3+ or below only on FM2/FM2+ and the soon to be released AM4 (hopefully)