Xmas is coming and I'm going to build my brother in law a new computer. Most likely everything will be new. Main thing is, I'm going to tear down his somewhat old computer and use the cpu,ram,hdd,and gfx card and build a CarPuter. It'll be relatively small, going to go in the front and create a center console for it. So now to the main question!!!!!!! When I play music from the PC to my Headunit, do you think sound quality will be effected? Do you think a better sound card will help create better sound? Just wondering.
I assume you will be using an analog input on the HU (such as rca inputs or headphone jack input). If that's the case, then yes, you will lose SQ compared to a CD which is digital. In your setup the computer would have to convert the digital music to analog, output it through the sound card, then your HU would have to process the signal and output it to your amp(s). When playing a CD on the HU, the digital music is converted to analog by the internal digital-to-analog-converter, and sent to the amp(s), so signal only goes through one conversion. Every time you convert digital to analog or vice versa you lose quality. Now, if you have a very high end HU with a digital input, and a high end sound card with digital output, then you could do what you are wanting to do with no loss of SQ.
As for your question about sound cards, yes a good sound card will improve SQ. IMO creative sound blaster are the best sound cards out there.