Are you planning on any autocross or rallycross, or just plain fast-road driving? If so, put all the stock parts back on and get a 5 speed L or make the investment up to an RS. If you just plan on daily driving and maybe drag racing some, the auto will be fine if you don't mind.

Bascially, anything that ever came on an automatic tranny Impreza from '93-'01 will fit your car. Want anti-roll bars? Go to Pick-N-Pull. Want 16" wheels and bigger brakes? Same thing. Want go-fast engine parts? Pretend you have an RS and try places like SPDtuning.com, subaruparts.com, and tons of others. Intakes won't match but from what I have heard headers and exhaust for the 2.2 and 2.5 are basically the same. If you live less than a few hours away, call the Subaru branch of Rancho Cordova Specialized Recyclers. This is the "junkyard of the Gods" mentioned by Dave Coleman in Sport Compact Car. They probably have at least one of every part for every car made in the last 30 years, except for some things you just don't really get at junkyards. But you could probably get everything you need to upgrade an L to an RS for maybe 800-1000 bucks. If you do, take pics and share your ride, because that would be pretty cool.

EDIT: Oh yeah, you asked about the struts. Short answer is yes- the US-market RS suspension is the pre-'01 WRX world-market suspension. Will that meet your needs? If you want to step up past that but not get spendy, get the STi parts for an RS and install a rear anti-roll bar. They are fast on 'real' roads and retain a good ride too.