Well, it's been a number of days since the Fubar IV arrived, and I've put it through its paces with a variety of different music. I'm feeding it with lossless files out of iTunes via the optical out of my iMac, through an Ixos toslink cable. The cans I'm using are Grado SR80i's. I have to say, I'm really very impressed. I've noticed a steady improvement as the Fubar has got itself run in, and the detail I'm hearing is incredible. It's a good warm, round sound from solid bass through to well-defined treble. It does show up poor recordings, but with a well-produced album it's giving some excellent results. I've been noticing lots of extra details that I'd never really heard before, even in albums I know really well. The separation of different parts is superb, and it's very easy to pick out an instrument and follow it through a track - but at the same time there's a really nice cohesiveness to the sound overall. I'm used to listening to my music through my separates hi-fi, but I can honestly say that this little set-up is blowing it out of the water!
I've yet to set up the Fubar with my Airport Express - to date I've left it in situ with my iMac as I seem to be getting more listening done that way. I may yet change this, but at the moment I'm having too much fun with it the way it is.
An excellent purchase - quite the bargain all things considered. I'll certainly consider the Supplier at a later date, but even as a standalone unit I'm really pleased with it. Thanks to all of you who recommended it.