Used GTX1080 or New VEGA 56?

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I recently upgraded an old system to brand new mother board/processor/RAM combo, but I stuck with my trusty AMD RX580 Nitro+ GPU, thinking I'd be happy with that. But I've now got a bit of an itch to upgrade that as well, as I'm running a 1440P/144Hz display (Freesync) and it's starting to struggle a little in some of the games I play (think UE4 engined stuff), even with the new CPU. I'm guessing the GPU is still a bit of a bottleneck.

I was going to take a punt on a well priced 1080 (not Ti) that I've seen for sale second-hand for about £300; but, it's several years old, already has had 2 owners, and has no box, or warranty. So perhaps a bit of a risk.

Conversely, OcUK have a Vega 56 card for £20 £15 more, new.

Some considerations I've been mulling over:
- My monitor is Freesync. I know Nvidia has just recently announced their cards will be supporting this, but I'm wary of how well it will be implemented, and therefore should I stick with AMD if possible?
- I'm unlikely to game at more than 1440P/144hz. The monitor is barely a year old, so I'll have no interest in upgrading for a long time. So blistering performance for 4K games isn't required.
- Not interesting overclocking the GPU, so whatever I get will be run at stock speeds.
- I know that in terms of raw power, the 1080 beats the Vega 56; that said, I'm just looking for a decent upgrade to the RX580 to better perform at 1440P res, without breaking the bank.
- I know AMD Vega cards have a rep for running hot/drawing power. Is this a serious problem if I'm only interest in running stock.

I'm a little out of the loop regards GPU tech, but I'm also aware the next gen AMD GPUs may be out soon (Navi). So would it just be better to hold on, keep using the RX580 and wait for that in case prices of current cards drop?

What would you do?

Other specs if it helps:
CPU: i7-9700K
RAM: 16GB DDR4
MB: GIGABYTE Aorus Pro.
PSU: Antec HighCurrent 620W.

 

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If you need the card now, go for the new Vega 56 for the warranty. Do you know if it was "2 previous owners" or "2 careful previous owners" for the 1080?

No idea really. Which is one of the things putting me off. I'm not desperate, but saw it come up and was interested, and usually I wouldn't be bothered about second hand goods.
But, it's quite a chunk of money for an old card with no guarantee...and then saw the Vega for a few quid more, which gave me pause.

I think it'd be Vega 56 for me (and it probably will be me shortly)

Leaning toward this if I'm honest. The current RX580 is still a decent card, and just over a year old (it was an RMA replacement for a failed RX480), so I could sell it on to offset the cost of a new Vega somewhat.

 

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What is the price difference and promotional offers on both cards? I'd be tempted by a 1080 tbh, unless there is a compelling reason not to?

The compelling reason is really just the fact that the 1080 is going to be second hand with an unknown history (and the face I already have a Freesync monitor, so the worry about potential incompatibility).
The Vega 56 is the Pulse one on OCUK....£315 down from £350, and includes 3 free games.

 

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Hadn't considered selling the games, that sweetens the deal a little more. Vega it is then. Thanks all.