Uploading HD videos to YouTube?

So far I've uploaded 4 different videos to YouTube using Sony Vegas. But for the life of me, no matter my settings, the quality is absolute sh*t.. Even when selecting 720p... All I want to do, is take an MP3 (256kbps), or WAV (44100Hz, 256-point sinc [VERY high quality]), and put some pictures (1024x768) to it... The files I import into Sony Vegas are of extremely high quality as you can see... I must be as dumb as a loaf of bread... I've even heard claims of people using Windows Movie Maker to upload HD movies (not too sure about that though)... If it helps, I also have the Adobe Master Collection as well... Basically, I want the music to sound as good (or as close to it as possible) as it did before uploading it to YouTube... Can someone give me some steps to get these videos to upload to the highest quality attainable?