If you're building a modeling amp, this might be a valid approach. You want the speaker to be neutral, just like in hifi, so the sound characteristic of the DSP generated tone is reproduced faithfully. But a hifi speaker won't give you any "bite" or "crunch" or any of the other sounds that are unique to guitar speakers. They have varying breakup characteristics, and guitar players often pick them to give them their own unique sound.So it depends on what you're tring to do. If you want to set your sound by modeling, use a neutral speaker and set the processor to create whatever sound you like. If you want to set your sound by choosing different guitar, amp and speaker combinations, then a high fidelity speaker is proably going to sound to "sterile" and boring to you.