Thanks for the replies, guys! @cynicrf @MisteryAngel @Dissentient @anon43920604 @lucimon97 @yeehti @mouf
A 970 would be in my budget but I don't want to blow all my money on "just" a GPU. There are other things I want to upgrade/replace too (finally an ext. HDD for proper backups, replacing my old Samsung HDD, maybe get a cheap SSD for games, new keyboard, DAC/Amp, open-back headphones, maybe a new case, mousepad, etc.). As I mentioned before, I might end up not buying a new GPU at all.
@mouf So far I haven't encountered any problems in games with my i3. I don't play the "newest" games, where some of them require at least 4 threads. I somewhat know the limits of my hardware and because I want to play my games at least at high settings I stick to older and/or less demanding games. The only time where I really wish I had a better CPU is when I use Handbrake for converting my DVDs/BRs from .mkv into .mp4. Other than that I feel like I'm fine for now - regarding the CPU (maybe WoW could do better, since it's very CPU-heavy). I already think about possible upgrades but am still not sure if I should - when I want to upgrade and have the money for it - got Skylake (or Zen if it's out by then and doesn't suck) or stay on Haswell a bit longer with an i5, i7 or Xeon.
@cynicrf I'm asking this question because before the 900-series was released I've read a lot that people shouldn't go for the variant with the higher vRAM but for the next best model (e.g. 770 2GB vs. 770 4GB -> 780 / 270X 2GB vs. 270X 4GB -> 280). I'm aware that games have become more demanding (and if it's only because they are poorly optimized/programmed).
@lucimon97 And there lies the problem: "probably still fine with 2GB" for now, but how much longer? I dont know when I'll be able to get enough money that I can even consider using it for a new GPU. 2GB seems already the bare minimum for gaming. I've been gaming on low/mid settings for years (crappy 8600GTS), I don't want to go back to that situation again where I can't play games because my hardware is too weak or only able of putting out low settings or even 768p/720p.
@MisteryAngel I only use the presets in the settings menus. Only time I "tweaked" the graphics was in Skyrim with texture packs.
@mouf Of course. I don't understand why people would - let's say - buy two 960 or 380 instead of a single 970 (you can get even a 980 for some of the prices of two 960s) or single 390X (and with a few bucks more the cheapest Fury). I absolutely agree. Unless you're already getting the best card on the market and want even more power (Fury X, 980Ti, Titan X).
@anon43920604 Nah, I could get one right now, but I don't really want to spend that much money for one part of my PC. And exactly as you say: it's powerful, but the 3.5GB issue would bug me (even if most of my games never fill up enough memory to experience the gimping).
Thanks a bunch for the replies! Prices seem to be a over the place as of right now, ~200€ (+/-20€) aren't realistic for 4GB variants of the 960/380 (I prefer ordering from Amazon since they don't charge a fee for paying like other places do and sending stuff back under warranty has always been amazing). And then there's the old "which one should I get?" dilemma (brand, model, which has the least coilwhine/is overall very quiet, etc.).
But thanks a lot for the information!