Before we can think of a conclusion we need to check the system costs and performance. While 100MHz do not count for much, it's clear a quad-core is superior, especially in games. The Athlon II X4 620 still outperforms any dual-core even when clocked 300MHz slower. Even when the dual-cores are overclocked to 3.80GHz, the cheapest AMD quad-core can still hold its ground and considering the power-consumption it offers far superior performance. For our system we choose the MSI 785GM-E65 board, the cheapest 4GB Kit for 1333MHz CL7 we could find and the cheapest HD4850 1GB which will result in a decent system.
Considering AMD's pricing for these CPUs, we must say that they perform rather well. However, energy efficient CPUs do cost about 30% more than regular versions. When you have a very cheap board which does not support any form of under-voltaging then this is the CPU to go. If you are gamer, we suggest you get a quad-core. Most games which come from the X-Box 360 and are ported to the PC-platform do support three cores, so an X3 435 for about €62,- is a better option. The downside on the three cores is the quite high power-consumption compared to any real X4. Of course some boards can unlock the fourth core, but you can never be sure it will work.
As long as you are a casual gamer, mostly surf the interweb, watch videos a dual-core is really not a bad choice. The Athlon II 245 is currently available just shy of €50,-, while the 240e costs about €64,-. Meanwhile, the Athlon II X4 620 dropped in price to about €77,- which is not bad either.
AMD has much work ahead. We think AMD could lower the TDP of all its CPUs by decreasing the VCore. As our under-voltaging tests prove there is quite a lot of headroom. The energy-efficient CPUs can go even lower as we have proven in our tests. We were impressed with the overclockability of the 240e, which also managed 3.80GHz but at a much lower VCore compared to the 245. From a price/performance point of view the Athlon II X4 620 is superior to any dual-core CPU and we still recommend it.