i use my Boss gt-3 in line/direct/mixer mode running through my pc sound card, connected to a stereo power amp (60w/channel) with about 10 speakers + a 200w subwoofer. awesome sound quality for all kinds of guitar tones, and it's great for recording, since i hear my sounds exactly as they'll be in the final mix
versatile as hell, and i can play fukkin loud if i want
this setup totally kills my Ross 100w guitar amp by far, and that's a good amp. i dont like having all my sound coming out of one little (or big) speaker box....
i dunno what a standard stereo PA would give driving a couple of marshall stacks..... hmmmm.. should be interesting