I really like this mod because it's cheap, easy and effective. And thought I'd share for anyone who thought it was cool. But gee wouldn't it be nice to find one that worked for Subarus 
Used, but Relatively cheap/easy. A good start. H6 or legacy turbo rear upgrade, and it's gonna be a balanced system. That's what I run. Pedal feel is a little soft, but without ABS, a little extra modulation/pedal travel adds some safety overhead.
WHEELS/BRAKES/SUSPENSION
LGT/STI/WRX/FXT BBK racing brake kit w/ 13" rotors/pads - 750 picked up
STI master cyl - 60 shipped
I love me a brake/suspension discussion. SSBC
used to make Big brake kits for subarus but a cursory check on their website doesn't show them anymore. They were pretty inexpensive for fixed-caliper 4-piston units. The cheapest big brake kit solution for most subarus is still probably the 4th generation Legacy GT calipers and rotors. For 07 and older imprezas, you need the Kartboy adapter bracket that they sell for the 'red' 2-pot rears. They're heavy, but all 4 rotors are vented. The front rotors are bigger than the red 4-pots. Throw in some stainless lines, aggressive pads, and you have a pretty good OEM engineered setup, that won't stress most of subaru's OEM master cyls. The main downsides are weight, ugliness, and sliding caliper versus a fixed unit.
As with any mod, you have to figure out what you're gonna use the car to plan for brakes that will fit your application the best. I like the "Reds" for a street setup(so you can still run 16" winter tires) and autocross. Brembo take-offs are huge cash and just to add unsprung weight and higher cost of pads/rotors over the life of the units. You used to be able to find better deals, but now, not so much.