I've got an old pair of 2-way Paradigm bookshelf speakers, which used to be my wife's home stereo (they're maybe 15 years old). I used to have them hooked up to a cheap Sonic Impact $40 box that has a Tripath "class T" amp inside (now available under a new name: Dayton DTA-1), but while the sound was good, the setup was prone to 60Hz hums and other assorted unpleasantries of cheap-ass electronics.

I switched to good headphones (Grado SR325is), got a swanky class-A USB headphone amplifier (CEntrance DACPort), and haven't used those speakers for a few years.

I decided, for fun, that it was time to resurrect the speakers again, so I poked through Amazon and found this Topping TP32 box. It's a two-channel Tripath "class D" amp, allegedly 15W/ch at 4 ohms and 10W/ch at 8 ohms (probably the same Tripath chip as the original Sonic Impact amp I was using), but with a built-in USB DAC, and what appear to be quality components (e.g., gold-plated banana plugs). It can drive two speakers and a pair of headphones (even at the same time). All for roughly $150 at Amazon, shipped direct from China.

I've got it hooked up now. It's officially good enough that I can differentiate the crappy sound from random BitTorrent things I've downloaded. Playing high quality lossless stuff from my collection, it's basically what the doctor ordered. Bass is strong but a bit boomy, leading me to wonder whether they've got their equalization wrong or whether these speakers are just a bit boomy themselves and have just never had enough power to push bass through them. Even at uncomfortably loud volumes, there's no audible sign of clipping. There's plenty of power.

It's not easy for me to do a controlled speaker+amp A/B comparison to really understand the source of the boominess, but I can do a controlled test of the headphone amp, switching back and forth between the CEntrance and Topping with my Grado headphones. I didn't try to do it blind, but I'd say they're close enough that I, and most others, would have a hard time differentiating. Both have low noise floors, strong bass, and exceptional treble detail. One thing that is easily differentiable is that the CEntrance has an analog volume knob and its a bit scratchy when you turn it. The Topping has digital volume buttons. No noise. Also, the CEntrance gets quite toasty when you use it (having a class A amp and all) while the Topping stays cool and quiet (class D amps being like that).

Summary: as a headphone DAC/amp, the Topping is fantastic. To drive bookshelf speakers, it's got plenty of power, but I'd need to do more experiments to sort out whether my problem is that these speakers just aren't so hot, or whether there's something up with the amp. I'm leaning toward the speakers being less than awesome. Of course, for most computer uses, it's completely irrelevant. If I want über quality, I'd use the headphones, or head downstairs to the big TV and big speakers.

Topping TP32: recommended for your desktop computer speaker needs.