Monitor - I have no experience with this monitor so I don't know what to tell you. I have a Samsung Syncmaster 955DF. It's flat and the quality is pretty good but I feel a little more eye-strain than my previous 17" Trinitron.
Mobo - Socket A, as has been already mentioned, is the way to go. Slot A has reached the end of the road, so Socket A will be a far better decision if you ever have to replace your CPU.
RAM - I don't know much about ECC but I heard it'll slower than non-ECC. Anyway, that feature is made specifically for servers so forget about it and save some cash. Get CAS-2 if possible.
HD - Nice choice, I personally just got the Maxtor DiamondPlus 40 GB so I'd recommend that if you want more space, but this is a great, fast, quiet drive.
Speakers - I would reconsider, I was looking at these at CompUSA and while they do look good, the quality doesn't do it for me. If that's not a concern and you care about looking "unique", then go ahead with these but I would look into a 5.1 setup if you are watching DVDs or playing games, or an Altec Lansing model if you just want two speakers and a sub.
CD-RW - I heard Plextor was the name to go with in burners. I can't really talk because I have some old-ass, p.o.s. Memorex 2x. But I'm considering a CD-RW myself and the new models sport some Burn Proof technology.
Sound Card - I haven't checked the price on this, but I would go with the SB Live! Value if the price is similar. If you want BOTH digital in and out go with either the X-Gamer or MP3+
Video Card - Everyone's gonna tell you to get nVidia. If you're gonna play games at all go ahead and get that. The GeForce 2 MX will be available widely by the end of the month, and that will be ~$120. I've also heard very good things about the Matrox G400 (I think that's it) - it's highly regarded for 2D graphics.
Your best bet is to look around. I wouldn't restrict myself to one place, different places will have different deals. If you are buying in a B&M store consider tax. If you are buying online consider S&H, though there are some sites that offer this free. Also look to see if you can get any coupons for sites that you visit. Good luck!
-mosdef