This thread has gotten way to confusing for this poor guy. It's his first build and you guys are taking about 12V rails. LOL
When you're a newb, you need newb terms. I was a newb once, just like everyone of you.
PSU's that come with cases are always, cheap/low quality.
The MOBO that I recommended earlier has Onboard (video, audio and lan) somthing you said you are looking for. You can always buy & upgrade to a videocard later.
400W Power supply is more than enough for your needs. Don't worry about future upgrades with that system. Building one like that will limit your need for more POWER.
Floppy Drives aren't used very much at all, that is true. They are used a lot in troubleshooting and emergency situations. They are so cheap it's not even funny. $8.00 It's better to have one and never use it, then need one in a pinch and not have one. Think about it.
PM me if you need any more adive, i'm glad to help you.