I am about to buy an external audio device. To my knowledge, this is the best device you can get for a similar amount of money... you can spend a lot more money to get something about as good, or spend less money and get something worse.
The device is called an O2 amplifier plus ODAC. It was designed by someone who went by the name of "NwAvGuy".
The O2 is a really clean analog amplifier, and is actually open source hardware. You can get the parts list, order the parts yourself, solder everything together, and have your own O2. You can pair it with any DAC, but NwAvGuy also designed a DAC called the ODAC. He(?) said that he would have liked to make the DAC open source as well, but it wasn't practical.
I will buy mine from a company called JDS Labs. They sell a single nice integrated device with O2 and ODAC in one enclosure.
There are audiophiles who sneer at the O2 because it doesn't cost enough. At my previous job I spent hours listening to music on an O2 with Sennheiser 650 headphones, and I want to be able to listen to music with that level of quality again. I am willing to spend my own money to do it.
I thought about buying a really nice DAC but I always hesitated to spend the money because it can be hard to figure out what is worth the extra money, and what is just extra expense. I am friends with a world-class audio geek, and he agrees that this is a good quality audio device. If you want top quality and you are spending your own money, get or make an O2.