The best ones are high end amd if you can get one cheap an r9 290x or 7990 would do the highest kh/s. But a good beginner card would be a r9 270 it will do about 450 kh/s also scrypt mining still has cpu viability and intel seem to do better.

A i3 or i5 with more cores and threads the better. Don't expect super high kh/s from cpu but since you can't run a miner on just a powered video card and you need a full running pc to do it you might as well have 2 or 4 cores tossing a few extra kh/s on top the gpus.

The intel line can also use less electricity produce less heat.