They might be, but considering the price of the GTX760 and that it performs like a GTX670 what is the point of even considering them?
- If you cannot find a GTX760 for under $300 then you are being ripped off
- If your local PC shop says they don't have them in stock, take your business elsewhere, don't spend money on low end hardware out of guilt.
Sure 2nd hand deals might be good, but the main goal of 2nd hand (to me anyway) is to build an awesome machine with ISA slots (that support DMA) so that you can boot into PC/MS-DOS, Windows 95c, Windows 98SE, Win2K, WinXP, etc. and play games in DOS that require a 'true' Creative Sound Blaster 16 / 32 AWE card, etc.
Investigate a little and see what the total cost is between such systems and the total expected performance.
- Doubling the money put into a GPU or video card does not double the price of a low end system, it may however double the performance... resulting in a far superior price/performance ratio by spending a little more on just one part.
Since the performance is better, the system runs better for a longer period of time; therefore the slightly higher upfront cost is spread over a longer life-time of the machine.
So you might spend +28% more (in total system cost), but if it lasts 3 years instead of 18 months you've actually saved money by not having to perform upgrades to keep the system going.
This all depends on what you are planning to do with the system of course.