10% or less is OK for cpu background usage.
1)The cpu's turbo boost(avg) is lower than the base clock. This can mean:
-Cpu thermal throttled.
-C drive was carried over from an older build, and you did not clean install Windows; you're still running chipset and registry drivers for the old cpu/motherboard.
There might be more, but I wouldn't be familiar with them.
2)Kingston A400. Dramless SSD. Very attractive pricing, but the performance tradeoff is not worth it.
Capacity too small, and it's too full.
The performance of a dramless model falls off earlier than it does with one that does have a ram cache.
For example: if a normal one starts to slow down at around 80% of its capacity, then a dramless one drops off at about half that, thus you need to get a higher capacity one if you go the dramless route.
There's the mixed ram thing too, but the biggest flags I can see are the 2 I mentioned above.