I don't think there is a significant improvement going from 2133MHz RAM to 2400MHz RAM. Probably at most a 2 FPS increase in performance. If 2400MHz does not cost too much more than 2133MHz, then go for it.
The Radeon HD 7660D is a little more powerful than a Radeon HD 5570 and much less powerful than the Radeon HD 6670. Still, it should be adequate for playing most games at 720p with medium graphics.
I think Richland desktop APUs are being released in June (2 month after the laptops). So if you can wait then wait. Richland will only be an incremental refresh of Trinity. Not sure what the iGPU performance will be. I'll guess a 15% - 20% increase in performance. The still makes it less powerful than the Radeon HD 6670.
Kaveri isn't expected until possibly Q1 or Q2 2014 so that can be anywhere from 9 - 15 months from now. It will be a significant upgrade from Richland, but again performance is unknown. If the iGPU can equal a Radeon HD 6670 then that would be impressive.