The audio out on your dell monitor is just pass-through from your computers soundcard, or videocard if you are using a discrete videocard.
You need to compare the sound chip from your soundcard to the audiochip on your videocard... since the videocard more than likely uses a realtec sound chip also, you need to compare those.
If you don't use a discrete videocard, but are using the onboard video on the motherboard.. then the motherboard's audiochip is what you are using, regardless on if you have it running through the lcd monitor or not.
the lcd monitor does not contain a sound chip.
the dac on the motherboard's videocard hdmi output converts the signal to analog for the lcd which passes it through to the speakers.(DAC= Digital to Analog Converter)
While the GPU does have an audio chip, it does not have a DAC. The GPU (or mobo) handles the basic audio processing in tandem with the CPU, then sends the digital signal to the monitor, which handles it via the built-in DAC.
In fact, when plugged in via HDMI, your monitor will show up as an audio device and can be configured independently. I've used two monitors with these DACs, the Samsung S27B550v, and the BenQ GW2750HM. Both had the same 24-bit, 48khz limit. Technically speaking, the Realtek ALC885 that I own should be superior. However, motherboards and monitors have their own digital noise (neither places priority on the DAC over other purposes), so you'll need to experiment.
In my experience, the Samsung DAC was horrid. It picked up a lot of noise from the monitor if brightness was below 96. It was audible over the built-in speakers, messed with sound over dedicated speakers, and blasted my ears over headphones. It was unusable and I experienced this on both S27B550v models that I tried. The BenQ has no such issues. The audio quality seemed to be comparable over 2xDayton B652 speakers. In this case, I found it useful to disable the mobo audio via the bios, remove the drivers, and then ensure they were cleaned using CCleaner and DriverSweeper. It's a little less overhead for the system.
So basically, plug in your HDMI and try it out. Once plugged in, make sure you open your control panel, go to audio devices, and configure the monitor (as most default to 16-bit, 44.1khz and need to be adjusted). If the sound is good enough for you relative to the onboard, then you can do as I did. If you find it lacking, then don't use it.
Thank you for backing me up on the fact that the monitor has a DAC! lol
you would actually have to disassemble the lcd monitor to find out exactly what dac is in it..