I've considered selling my 04 WRX with 64k miles, prices I've been offered from garages are £5,250-£5,500.
The saloon comes in 3 guises, AFAIK:
GX- lacks the bonnet scoop and- I think- the turbo. 0-60 in 10s, fairly slow.
WRX- the base level performance Scooby. I have one and love it. Punchy but also comfortable.
STi- goes like the clappers. Some styling additions, but mostly under-the-bonnet improvements over the WRX. The highest insurance group, mind.
2003-2005
£245 for 12 months. The hawkeyes and hatchbacks are £200 more, as they're after 2006 (there's a cap for cars registered before then, which the blobeye falls into)
Nothing special, in my experience. Check the usual stuff- listen to the engine when cold, check the oil, get a HPI record etc... Squeeky seatbelts are the most annoying thing but it's normal!!