I just wrote a MB article for P4 supporting boards (and Athlon), there's lot of good info in there. Whatever you do, make sure the board you get is a socket 478 board and not socket 423. Also, get either the i850 or Sis 645 based board. (The Sis board uses much less expensive PC2100 or PC 2700 DDR SDRAM, and not Rambus PC 800 RDRAM.) Don't get the PC 133 SDRAM based i845 board, those are terrible performers.
That particular Asus board has a good reputation. I think you would be happy with it.
I don't really have much to say on sound cards. Soundblaster Live! cards are pretty much the standard, but they *can* be a pain to setup. (Creative's drivers are not that good.) Unfortunately I don't have any firsthand experience with any of the alternatives, but there are other choices out there now. Hopefully someone else will chime in on that one.
(I'm not even going to get started on the AMD vs Intel CPU debate. You asked for opinions on that rig, not which CPU a better choice.
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