I'm glad you mentioned that. It seems that a lot of people are questioning the value of higher res music on the basis of the quality of their remaining high frequency hearing ability. At my age, I certainly cannot hear those high frequencies. But to me, the advantage of higher res, whether music files or lossless movie codecs like Dolby TrueHD or DTS HD Master Audio, is that they sound smoother, as you say, and more organic and natural in the mid range. Things like massed strings and voices.
As to using your laptop, that is what I'm doing with my HP laptop, feeding my PS Audio Stellar Gain Cell DAC/pre-amp via a relatively inexpensive Supra 2.0 USB cable. Before I got the USB cable, I was using an analog interconnect from the laptop's headphone output to an analog input on the PS Audio. I can say that using the USB cable is superior in every way to the analog interconnect, which leaves one dependent on the DAC in the laptop. Via the USB cable, the sound is much more clear, dynamic, and immediate sounding.
I will say, perhaps because of the PS Audio's clarity and accuracy, the sound seems fairly "bright" and certainly not a euphonic sound at all. I don't think I can blame that sonic signature on Amazon's service. Amazon's HD and UltraHD tracks are quite clear, with good sound stage and imaging, vocals are placed well across the stage, and you can hear multiple vocalists nicely. As I only just started using the DAC section of the PS Audio, I'm going to wait some time before making any further judgements on the sound. I'm not sure I buy into "break in", but am going to give it some time nonetheless.