This is what the OP said :
"For an upgrade the card has to only require at max 1 6 pin pci-e or 1 8 pin pci-e.
The requirement in the OP is artificial. It is not a hard requirement.
His PSU is a 450W unit that already has a single 1x6-pin connector and handles a CPU platform that peaks at 305W under load or more. A 2nd 4-pin molex to 6-pin adapter can be purchased for $5. His PSU is clearly capable of huge loads on the 12V rail.
There's nothing in here about "throw out my system and buy a 4 year old sandy bridge so I can run an R9 280".
That's what the forum is for - to provide alternative ideas, which may in fact be better than the proposed solution.
The main reason a GTX 960 is perfect for his setup is that he has a 5770 - almost identical power draw to a 960.
That's the problem. You provide a recommendation without talking about any of the cons of your proposed solution. I've seen you completely ignore the cons of the 960 despite many experienced gamers pointing it out to you in the GTX960 thread.
1. GTX960's frame rates do not equal good frame times. In fact, while 280X is just 15% faster than a GTX960, the frame times are worlds apart in favour of the HD7970 chip. You have ignored this since day 1.
The frame times matter a lot more for smoothness and this is where 960 falls apart against the HD7970 style chip.
http://www.techspot.com/review/948-geforce-gtx-960-sli-performance/page3.html
2. GTX960's 2GB VRAM is a major limitation (this is already related to 270X which I pointed out). Titanfall, Watch Dogs, AC Unity, Shadow of Mordor, Evolve, Wolfenstein NWO, and the list will continue growing over the next 2 years. You have ignored this since day 1.
And now the brand new Evolve:
http://www.sweclockers.com/artikel/20031-snabbtest-grafikprestanda-i-evolve/3#pagehead
It's only going to get worse for 2GB cards, much worse.
This whole argument of getting a GTX960 to save some power over a used HD7970 3GB is undermined when the OP could sell his X6+mobo, get a Core i3+ mobo with the $80+ savings from not getting the $200 960. With this strategy, he'll get a way faster CPU and much better GPU for games, not to mention the much needed 3GB of VRAM.
It seems the OP doesn't want an in-between system and just either wants $500-1000+ Skylake-E with NV Titan style GPU as his next upgrade. I don't agree with this way of thinking as he will still use this system for the next 2 years and selling the AMD parts and getting an i3 or esp. a used i5 is a major benefit that will drop his power usage a lot more than the 960 can. If you want to save power, why would you want to leave a 300W+ core system that gets beaten by a sub-
90W Core i5 system?
89W i5-4460 system > 305W Phenon II X6 @ 4.2Ghz in games.
Finally, am I supposed to believe that someone who is looking to buy NV's Titan-esque style GPU and a Skylake-E platform down the line can't afford to buy a $40 XFX 550W PSU, sell his X6 parts, but a Core i3/5 system, and spend $40 extra over the 960 for a 45% faster R9 290 (as an example) to transform his outdated rig into a powerhouse 1080P gaming system for the next
2 years while he waits for SK-E? This thread is "upgrade or wait", isn't it?
I vote upgrade for now and upgrade again in 2 years. This argument of not wanting to buy "old parts" is odd because the X6 is ancient so it's not as if pairing that CPU platform with a 2015 GPU will magically make the system up-to-date. It won't. In fact, I bet he doesn't even have a SATA 3 SSD in there that can take advantage of modern SSDs.