Just wondering how you can physically plug a 4 pin and a 6 pin into an 8 pin socket.
The only six pin connector you would have would be the PCI-E connector for a graphics card and its not a good idea to use that in the cpu power socket.
Yes you should have the 20+4 connected to the mobo power connector.
If you don't have an eight pin connector then it should run off just the 4 pin but you won't be able to overclock is my understanding.
The pc will not boot without at least a 4pin connector plugged into the cpu power socket.
If you provide a budget then me or another member will reccomend a suitable psu for you.