Sitting in my study this morning, listening to some Chemical Brothers, it occurred to me that I could use a bass bin for my PC.

So: I'm wondering whether there exists an amp that takes SPDIF and will output 2.1 audio (stereo + sub), that also has a (switched) socket for some decent headphones. I'd prefer SPDIF to eliminate analogue noise from the PC. I don't need input switching -- there's only one PC. I definitely want the ability to leave the headphones plugged in and switch outputs.

Of course, I could just use my spare empeg, but I like the media buttons on my keyboard...

Something like the NAD D1050 you mean? I personally like the NAD D7050 better, but for your intended purpose, I believe the 1050 is sufficient. And there's also the D3020

Edit: it seems it doesn't have a sub out.

USB->serial->empeg control.

I've posted here before about my adventures in USB amps. My current Teac A-H01 handily drives my massive VMPS speakers, each of which has a 12" woofer. The headphone jack is also very high quality. There's no dot-one line-level sub output, though I don't particularly need one.

The NAD D7050 does have a sub out and optical/coax in, the headphone out may not be switched though.

They tend to be quite big and a bit more expensive, but inexpensive Onkyo amp are still remarkably good.

I ended up with a low end Onkyo TX-NR for my home PC. Ii takes 5.1 audio input via HDMI, and it sounds great. And it has all the benefits of a good amp.

Interestingly, I later decided to connect my home server video output to it, and I ended up using it as a HDMI switcher. But that was not the initial intent and even without such additional benefit it was still worth its cost.

I remember I spent around € 200 on it back then, but I can't remember the exact model now (I'll check once at home).

However, it was a predecessor to this, which I believe costs cost less than $300.
http://www.uk.onkyo.com/en/products/tx-nr414-75913.html