I think your estimate is off.
GTX260 216 is at 81 VP (650 is slightly lower) while GTX750Ti ~ GTX570/480 which is 154-155 VP. That would make GTX750Ti almost 2X faster than a GTX260 216.
OP, the issue with the 750Ti is that right now it sits in an awkward pricing range and generally speaking it's not that great for 1080P gaming to keep for 2-3 years as you seem to want to do.
If you are trying to save $, then the
R7 260X 2GB is at least as fast as the 750Ti on average but costs
$80, while most 750Ti cards cost
$100-110.
From an overall standpoint, I think you should look at a class above such as GTX950/960/380/280/280X and preferably a 3-4GB card. If you do not mind waiting for deals, there will probably be more sales this holiday season on all of these cards. It just depends what your budget is; however since you waited that long to upgrade, I don't think I'd personally be happy with just 2X faster over your card. If 750Ti is roughly ~2X faster than your card, if you get a card 70% faster than the 750Ti for just $50 more, you'll be getting a card 3.3-3.4X faster than yours. In your context the extra $50 above the $100 GTX750Ti's price would provide an exponential increase in performance, while possibly landing you a 3-4GB card as well.
I would also suggest that you buy an after-market cooler. Most of those 920 CPUs can overclock to at least 3.6Ghz without much effort, some even go to 4-4.4Ghz with a solid air cooler. Even a
$15 air cooler on sale would allow you to hit 3.6-3.7Ghz on the 920. 920 is very easy to overclock as many of them can go to 3.8-4.0Ghz on stock voltage.
I think if you are patient enough there will be this quarter on a GTX960 4GB, R9 380 4GB or R9 280X 3GB for $150. The extra $50 over the 750Ti is well worth it. Alternatively, there are bound to be sales on the 750Ti for $70-80 as well.