Some more comparisons - with burn-in seeming to be finishedSorry if this is a little scatter brained, but I am exhausted.
So far the Nuforce Icon SS amp needed much less burn-in than my other amps (3-12 hours). It still sounds the same as this afternoon, and as it did when I went to bed. I only just started using it for headphones last night, and it sounds very close to my other SS amps now - being very nice sounding and with the advantage of being a better speaker amp than the Travagans Red. The Nuforce now seems to have just a little beefier mid bass/low mids via headphone out than the Apogee mini-dac of Travagans Red.
I still slightly prefer the Red as a headphone amp over the Nuforce, but greatly prefer the Nuforce as a speaker amp over the Travagans, except with electrostatic transformers the Red is also wonderful and they are close to equals. If you plan to drive speakers as much as phones, you might want to consider the NuForce Icon because the Red drives the speakers even when you plug in headphones (so you can plug a powered sub into the headphone out). You have to unplug the speakers from the red to listen to phones alone. The Nuforce cuts the speakers off when a headphone is plugged in, but it has a seperate pre-amp out on the back for the subwoofer - so your sub will keep playing bass while you listen to headphones. So, you'd have to turn off the sub manually when you listen to headphones if you don't want to disturb others.
However, all I had to try out as speakers was the small 2" Travagans speakers which needed a lot of EQ to sound average, or some Velodyne 2-way satellites that were designed to work as part of a 5.1 system with Velodyne subwoofer. So bass was lacking with both sets of speakers, unless I added a small sub I have laying around. Again, using the speaker out to drive Stax headphones sounds great, and it even sounds good driving my $2000 HE60 via Stax SRD-7 Pro transformer. But the Nuforce drives the Velodyne bookshelf satellites much better with more bass, and drives my electrostatics with a little more authority.
Nice features of the Nuforce. It has three inputs and three outputs - it has a USB DAC that I haven't been able to test yet; and has both a 1/8" line input and an RCA line input - plus 12 watts/channel speaker out, pre-amp out, and 1/8" headphone out. However, you can't roll opamps with it.
Nice features of the Red - it is tune-able with opamp rolling and sounds a little tubey with the OPA627 or AD797 opamps, and is a little more SS and airy with the AD743. With the OPA627 it sounded close to my Woo WA6 tube amp, surprisingly. The stock LM4562 opamp is very neutral and crisp and at least with the stock opamps the bass fills in more by about 250-300 hours. I like it with a wide variety of headphones even stock (the RS-1 were the only phones I didn't initially like with it, until it had 250-300 hours on it). It even does a great job driving my $1,500 Edition 9 headphones.
The NuForce Icon headphone out seems to be very close to the level of my Apogee mini-DAC headphone out, and to the Red with upgraded opamps. I am still in the process of evaluating the Nuforce, but in summary - the Travagans Red is probably more versatile in rolling opamps to match the sound to your particular headphones, and the Nuforce is probably the more flexible if you are replacing you speaker amp and also need a USB DAC (while still having a nice rich tubey headphone out, although you can't change the sound).
My take is that I can't part with either amp. I would not be complete without the NuForce speaker out into SRD-7 pro to make my HE60 punchier with more bass. On the other hand, my SR-003 absolutely love the Travagans Red when driven by speaker out thru SRD-7 pro, gaining more extension in the bass and treble with a good balance to the mids (not too forward, and not rolled off).