AMD APUs has never been a good prospect on PC gaming... It would run slower compared to say, an i3-6100, but it's going to be fine, it won't bottleneck.
Of course, it's OK to upgrade to a 950, there's nothing wrong with that. But, the thing is, it's not going to be that much of an upgrade, the 660 is already pretty fast. An upgrade to a Skylake system, even to a Pentium, seems like a good one. This will let you upgrade later. I can stay with the 660 for a while with that Pentium combo, and upgrade the Processor and GPU later.
Costs 170 quids:
http://uk.pcpartpicker.com/p/HkpyjX