hmm... id have to go with the 2000 si, for starters, its a newer car, granted the gsr b18c1 is a great engine, i doubt your gonna fine one that hasnt been "dogged" out, and the same goes for the si, but the b16a2, in my opinion, is a much better engine,and its only a 10 hp difference, 10 less hp for 4 years of wear and tear????i think its worth it, but its gonna come down to personal preferance... and condition of each car. just make sure you get and alarm, and get an auto-lock and some wheel locks :P