if u go the rb25, ur puttin heaps more weight on the front end of ur car, but, if u go for the rb20 ur gettin good bang for bucks and it dusnt weigh as much, basically NO-ONE!! would replace an sr20det for an rb20det, the performance is virtually the same...the only time u'd put in an rb20 is if u bought an older sil b4 the sr20's came out and it had a ca18de/ca18det engine in it....the only xception wuld probable be if ur sr20 blew up and u didnt hav the dosh too get another sr20 put in, bcoz the rb20 engine is a much cheaper engine to buy than the sr20........newai, imo u CANNOT deny a 6 ova a 4