I can't see a RB20 adding that much more, if any, compared to putting a 280zxt L6 in a s30. I have the 26 in my 260z with twins, and lots of extra added weight vs stock L6, and my car handles fine to me.
I'm not qualified to speak on what it would do as a track car though, compared to the L6. Street wise, it feels orgasmic....