Ok, so I took the plunge and got me Vegas Pro 13 to do some minor video editing, based on recommendations here.
So far, all I really need to do is replace audio and render the video with the new audio, which was unreliable in Sonar at best.
 
I realize this is not the best forum to ask this but since some folks here seem to use Vegas a lot, hopefully someone can answer me;
I have succesfully replaced the audio (actually I just added a new track and muted the coupled one), and now I want to export my file. In order to keep the chance of artifacts and quality loss through conversion to a minimum, I would prefer to stick to the same settings that my video file is. It's a .mov at 960x540x32, 25,000i so if I read that right it's 16:9 and 32 bit color depth with a framerate of 25. I click "render as" and I'm presented with what must be a hundred different options and filetypes. When I click "match to project settings" they all disappear. Looking for common container types I find MPEG-2, mp4, AVI, MOV, but none of them allow me to set the project settings like they are right now. I had expected all of this to be more or less automatic, to be honest. Can anyone advise me what the best way is to move forward? I tried to export to a relatively high quality MOV file but I had to set it to a different resolution and there was an obvious difference.

To elaborate; no matter which options I seem to choose, the file always comes out looking either blockier, with different colors, or waaaaay larger. Isn't there some kind of simple "keep original" setting?

Right click on the video clips and go into "properties" where you will find that option.  There are several videos on YouTube that explain how to render in Hi Def if you're interested.  Just google "rendering Vegas in Hi Def".

if you import the clip into a blank project, you'll get a dialogue that asks if you want to match project properties to the clip. say yes.
 
now replace the audip track and render to main concept mp4, changing the default values to your 960x540x32, 25fps. or to quicktime mov if you have a specific reason to do so. otherwise, mp4 is best.

Thanks guys. I did do the "match project properties" when I first imported. I've also since found a YT vid that recommends encoding to main concept mp4, which I did, the problem is the colors and contrast are different from the original and the file is about four times as big with their recommended settings. The original was a .mov. But when I use the Quicktime encoder the quality is even worse.

Also, check out the Creative Cow forums for Vegas, I've gotten lots of help there for my Vegas-related needs. Especially in regards to codecs and all that crap (I hate codecs)
 

Kinda off topic, but you might also check out *Handbrake* (you can google it), as it is a great compression for MP4, which is good for shrinking file sizes when you're done, and maintaining good quality too.  I use it all the time for YouTube and when sending MP4 files.

Handbrake is great, but I doubt it will givevyou better results than the encoder in Vegas. I would avoid any of the quicktime labeled settings since the better quicktime codecs like ProRes are probably not avaible easily on windows. I think it just comes down to seeing what works for others using similar workflow to you and trial and error.

You might want to change the color bits from 32bit floating to 8 bit in the project preferences.
 

Thanks again. Why would changing the color bit depth downward help?
I have and have tried Handbrake btw, it seemed like a basic converter/ripper, people recommend it to rip DVDs if you need to cut stuff in Vegas.