If you can stretch to it buy an EVO, I have had 3 of them, a 5GSR, a 7GSR and a 9GT in last 7years. They are reliable and trouble free as a rule. Obviously older the car/higher milage you may run into problems as with any car. Good power to be had from basic mods as someone said.
I sold mine due to work situation BUT when I get back on my feet again thats exactly where I will be going back to, hopefully an 8MR or RS or a 9Gt again or RS if I can find one. A 7GSR are good value at the moment and with basics like exhaust, fuel pump, an Evo 9 turbo 380BHP and similar torque. Spend time finding a good Evo, buy a pot and it will haunt you and cost you severly. Look on
Mitsubishi Lancer Register if you are intrested, very good site, lots of info, good traders and good helpful members.
Imprezas are trouble IMO and not small problems either, normally engine or pistons melting, dont matter if they are Type R coupes or WRX, wouldnt touch one with a barge pole from what I have seen of them with friends and people I know who work on them.
This was my 9GT before I sold it