Difference between '93, '95 and '97 Imprezas?

My brother just got a '93 and my girlfriend just got a '95 (both the Impreza L models). My brother's is the 1.8l fwd and my girlfriend's is the 2.2l awd. when i looked on ebay or some other sites for parts such as clear bumper lights, taillights, strut bars, exhausts, headlights, etc, some of them say 93-2000(?), some say 95+, and some say 97+, and some say they will only fit the RS models. so what is the difference between these cars that some parts fit only the newer ones or the RS model since they are all basically the same body style? i was also wondering if an RS hood would fit on one of their cars... somebody said the headlights and grill would have to go too but I just wanted to see if anybody could confirm that. Let me know if you can help me out.

thomas crown

i also have another post up if anybody is interested in helping me with a personal problem...
http://www.automotiveforums.com/vbulletin/t30633.html

thanks