Forward or laid-back sound has nothing to do with the frequency response balance and forwardness is far from the same thing as being "aggressive" which is what you seem to think is the same as forward. Pro900 is very aggressive sounding and XB500 isn't aggressive sounding, it's the opposite like you pictured it but it's very forward sounding though.
Aggressive = Frequency response balance related, emphasized mids & highs (especially range 4 ~ 12kHz). Often shrill/harsh and more tend to cause sibilance or ear-fatigue.
Forward = Soundstage related, engaging/fun/"in-your-face" or "on-stage" sounding, often leads to smaller soundstage. Picture yourself sitting in a concert hall, the closer to the vocalist and instruments the more forward sounding.
Laid-back = Soundstage related, lean/relaxed, "concert hall" sounding, often leads to bigger soundstage. Picture yourself sitting in a concert hall, the further away from the stage the more laid-back sounding.
Edited by RPGWiZaRD - 6/11/11 at 1:10pm