The spec for EPS12V states a 24 pin + 8 pin connector, but I've read some boards have only a four pin connector adding to the confusion.
As for getting a 4+4 connector to fit in an 8 pin connector it will only fit if the keying on the 4 pin plugs are correct, also you have to make sure both 4 pin plugs have ground on pins 1-2 and 12v on pins 3-4, and looking at some PSU specs they do, as the 8 pin plug has ground on pins 1-4 and 12v on pins 5-8.
4 pin =
8 pin =
even then you have to make sure there is sufficient amps on them to power the CPU, more so if it's a dual core as my ASUS board needs 16A and 19A peak for the CPU!
I think you're correct in saying the 8 pin ATX 12V is just a fancy name for 8 pin EPS12V as my ASUS board has that 8 pin connector labeled as ATX12V1, so I think they are one and the same.
That silverstone PSU will be OK, that 8 pin connector will fit the 8 pin connector on supported boards!