For me, a desktop amp is distinct from a regular speaker amp or a headphone amp.
A headphone amp is for headphones, unless it's a Ragnarock, in which case it can also do speakers just because.
A regular speaker amp is usually something you need to put on a shelf, in a cabinet or on a rack. It tends to be 17" wide, several inches high, and many inches deep. It's not something you put on your desk - it's too big.
A desktop amp is something small enough for you to put, well, on your desktop. It's not a huge block of gear that shoves your keyboard off to one side. It's compact with a small footprint. It's primary function is to drive near-field speakers on or near your desk, not giant Quad ESLs across the room (at first I thought that guy was being sarcastic, then I remembered the Quads were designed to work with 35W 303s).
By design, a desktop amp could also be suitable for small rooms, e.g. bedrooms or kitchens or tiny houses or small apartments, but it's not supposed to be a replacement for a 100 watt behemoth driving your Magneplanars. It's not supposed to drive a 15" sub.
A great sounding 15-25 watt A/B single-purpose stereo power amp in a Modi/Magni/SYS chassis for $250-300 would be an awesome thing.
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