I agree with the above sentiments in general when it comes to GPU upgrades. If your current GPU is doing the job, keep it until it's no longer doing the job.
Some people like the idea of a more efficient GPU, though. Usually I think that tradeoff isn't worth it.
HOWEVER...
In this case, the R9 295x2 is a 450W card. That's a crap-ton of power draw, along with the added heat, fan-noise, etc., that would be required.
I don't know if those prices you're seeing for used R9 295x2 cards are anywhere near reality, or the seller's wishful thinking. As mentioned by
@geofelt , the RTX 2060 is about equivalent in performance. Worth noting is that the 2060 draws about 160W. That's just over 1/3 of the power draw of your existing card.
Would I change one for the other? Maybe, if living in a state with pricey electricity, warm weather, and if the cooling-fan-noise and heat was really bothering me.
Another thing to consider is a used GTX 1070 (150W) or 1070Ti (180W), though, in those cases, the usual caveats and warnings of buying a used video card apply.
Side note: by the standards of today's high-end cards, 1920x1200 assuming 60fps isn't hugely taxing. What is your monitor's refresh rate? And, am I correct in assuming that it does NOT have either GSync or FreeSync?
If your monitor is 60hz, then, even the R9 295x2 and the above cards I mentioned are overkill, and a "downgrade" to a 1660Ti (POSSIBLY even to a 1660, both are 120W) would be all the performance you'd need to maintain 60fps at your resolution.
On the other hand, if you're planning to upgrade your monitor relatively soon, then consider putting off any video card upgrade.
(side note: I'd steer clear of 4k unless you REALLY need it, because 1: I'm a fan of ultrawides, but more importantly 2: more pixels = more taxing on a video card, and at 4k, only the 2080Ti can give maxxed out details on modern games AND maintain 60fps).