If you want to take advantage of all its capabilities, yes ... that's speaker IRs and power amp simulation, specifically. Some people run it into a power amp and guitar cabinet, but that's missing out on being able to dial in very precise power tube behavior (class a or class ab, bias, voltage starvation, negative feedback, etc., and the ability to switch through hundreds of speaker and cabinet combinations at the twist of a knob, not to mention how that cab was miked, where it was miked, the mic itself, mic distance, etc.
You can set up a basic amp block and get a wide variety of sonic palettes just by stepping through the cabinets ... 1x8 oval radio speaker like Jimmy Page used on early Led Zeppelin tracks, 1x12 open back, 1x15, 2x10, 4x12, 8x10 metal bass cone cabinet ... sky's the limit. People even set up acoustic guitar presets using an impulse response file from an acoustic guitar body.
I use K12s and K10s live and in my studio, they sound tremendous.
Another plus for the QSC is its two channels and 1,000 watts; I've used the second channel on my floor wedge K12 for my vocal monitor feed, and it works great on tight stages (or venues with crappy monitors).
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