Do you have a specific budget in mind? People will be able to give you a better idea of what you should get if you have a price in mind.
If you already have 4 pot subaru calipers, then the next step up would be second hand 4 pot brembo's or new 8 pot k sports. Both have the same size pad afaik but theoretically the k sport should be better with more pistons spreading more load although the brembo is generally better quality generally but you always take a chance getting stuff second hand. StiBrian has a set of k sports on his, upgraded from 4 pot subaru i think and he says there is a huge difference. JpTypeRA has done the same i think
The next step after that is AP Racing 6 pots or Brembo 6 pots. Think Yogi had the brembo 6 pots on his wagon when it was for sale so he might be able to tell you how good they are. Brembo and AP are probably the 2 best, well known brake on the market