[donsolo]

The best, most accurate audiophile speakers will be very flat responce.

And very few prosumer monitors are anywhere near flat responce (NS-10s being my example in the mids)

Also, good audiophile speakers (the floor standing ones) will have a deeper bass responce where it's hard to find prosumer "monitors" that go much below 45hz. The 603s don't need a subwoofer.

Really, it's about quality reproduction of sound more than anything. That means good dynamic range, even frequency responce, good crossover that don't alter phase.