[packtreefly]

I'd recommend any good sound device that connects digitally, like USB or HDMI/Displayport.

So the answer is that you should get a dedicated sound device, but don't bother looking for an internal card. External devices are easier to connect, won't complicate upgrades, and can be attached to a different machine with less work.

Onboard has always been good enough, it's just that people are usually willing to accept trash.

[tensility]

I'd agree with your recommendation while pointing out that a big part of the benefit from doing this is getting high-quality audio ADC/DAC hardware in the final mixed-signal interface. This can be achieved well with either kind of device, but the external device will be usable longer.

That said, my biggest gripe about external sound cards is introduction of drivers rather than usage of standard bus class protocols, which has a tendency to create "complicated upgrades" problems due to the manufacturer dropping support for the driver over time, causing an unnecessary forced obsolescence for otherwise good external hardware.

[nicolaslem]

The vast majority of audio interfaces on the market today are class compliant. They will work out of the box with any OS and even phones.