I haven't used the CX20671 but I have used Conexant before. I had one in an older desktop that shipped w/o a pci sound card. I was rather happy with it . I did end up putting a audigy (they were still new then). One of the biggest factors for quality of integrated soundcards is the design and layout of the MoBo its on and how they choose have conduits and data lanes travel on the MoBo. Alot of people will tell you integrated sound is complete trash, but thats not entirely true. Some are definately trash because of the MoBo design or because of the way the manufacturer uses the MoBo to fit in what they want on the board can also effect it. But some are not. Generally speaking in my personal opinion, desktop systems with integrated sound can be a little less noisy (and I mean by a very small difference compared to lappys) because most OEM laptop MoBos try to cram everything onto that board (Sata controller, wifi radio, integrated usb ports, power supply for monitor and vga, etc.) . But that doesn't make that much difference really, or hardly any. I am also willing to bet having your computer's internal drive be a SSD might reduce some of the residual "background" noise if your card is normally has a high noise ratio. Generally when I worked with most integrated laptop soundcards, amping is only required for high imped. HP, if you like your music loud, or trying to drive passive powered speakers. If you wanted to get a cheap DAC/soundcard that will boost SQ I would recommend the Turtle Beach Micro II or Amigo II if you need mic and line out. They run about $25 on amazon. For an actual DAC you would have to spend a bit more. I don't know how the Syba USB DAC (Actually just bought it for the heck of it seeing if it worked, its only $7.60 right now) but some people say that they a pretty good in terms of giving some boost in SQ, they use the C-media 119 chipset if my memory serves me right. So that one is not utter trash. Some people here recommended it for a quick replacement DAC if your on a real tight budget. As I understand its pretty good in its price/performance ratio. http://www.amazon.com/Syba-SD-CM-UAUD-Adapter-C-Media-Chipset/dp/B001MSS6CS/ref=sr_1_1?ie=UTF8&qid=1304878844&sr=1-1-catcorr
. Micro II and Amigo are on amazon too.
Ultimately what sounds best to you is what is best. That said I my favorite integrated sound card I have got to date has actually been an IDT chip. Realtek is fun to "play" with your media as they generally include a "sound suite" with the card.