HD Authoring software whats best >???

Sony Vegas. It's a full-blown editing suite, and can render (transcode) into both formats, as well as many others. Once you download the DivX codec, it becomes an available option in the render box. Obviously, it will also let you edit, cut, do color correction, audio correction, titling, etc. You can mix different file formats in the same project, even on the same timeline. It also works with raw HDV files, allowing you to capture without using hundreds of GB per hour. In the raw HDV format though, you won't have frame accurate editing, just the GOP, which is usually 15 frames I believe.

You might check out the much less expensive Sony Movie Studio. I haven't used that, but it's predecessor, Sonic Foundry Movie Factory, also had the ability to render in HD formats.

The highest resolution for DivX is currently 1280x720 (720p). WMV can do 1080i, not sure about 1080p.

I'm running a Barton 2700+ oc'd to 2.2 GHz (oooo... scary...). Working with the raw HDV files doesn't slow Vegas down at all. Haven't tried rendering yet, though. That might be a different story.