It does depend a lot on what your detailed requirements are.
Do you need particularly quiet, or does a sound like a hoover not bother you? Do you want to re-use disks? i.e. is IDE support important?
What form-factor do you want? Tower, mini-tower, desktop, micro desktop? How many HDDs to you want? RAID? How many CD / DVD / front-panel devices do you want?
I can certainly recommend a dedicated sound card - integrated sound is invariably crap. But you don't need the latest 7-1 thing from Creative - pick an older 5.1 one up off ebay for peanuts, and add a Creative front panel, very handy.
As a balance between performance / future-proofing / cost, I generally pick the 2nd or 3rd fastest currently available AMD CPU, then select mobo depending on the CPU selection and how many PCI / PCI-Express slots I need.
The number of PCI slots is usually important for me - so many things to fit, when you include sound and wifi (although that can be USB).
Don't skimp on the PSU - 500W min these days.
End of random musings
SD