No, you don't have to "deal with" them. You can safely ignore them. If you leave them at unity (0) gain they will do nothing. The preview bus is where sounds previewed in the browser are routed, so it won't have any effect on anything if you're not doing that. Same for the metronome bus. You can hide or delete them if you don't use them, and you can save a version of the blank template without them - or use one of the more basic ones provided - to start your projects from, if you never want to see them again. But they do in fact make sense and serve a purpose for some users, and you might find your use of Sonar gets more complex over time, so you might find yourself wanting or needing such functionality yourself at some point. Railing against it being there without, apparently, taking the time to understand it at all seems kind of self-defeating.  
 
 

You only need to set up a given template once.
 
Then it's there forever

I think you are over thinking this Djwayne. You use what you need to use and ignore the rest.
 
If you were using a hardware desk with 8 buses would saw off 7 of them if you couldn't use them? 

That's what I was doing, using just what I needed and ignoring the rest, and that's where I got into trouble. The other level meters that I wasn't paying attention to, were lowering my output levels. I'd export a track and post it to SoundCloud, and it would be very quiet compared to other tracks on SoundCloud. It got so bad I could hardly hear my tracks...I had to do a complete search thru my audio chain to find the problem, and I did find it in Sonar's mixer. Once I corrected all the meters the volume came up......but I was shocked by how many meters were in the default chain.

Well that's to be expected because every single bus has a pair of associated meters.
 
All of theses busses - assuming your audio is feeding each of them - should be showing the same level fluctuations & peak readings as you play your piece.

Not to keep adding on, but...  the Metronome and Preview buses are not intended to ever be included in the signal chain, at least not by default.  As mentioned previously they serve very specific purposes, but routing your tracks' audio to or thru them is not one of those purposes.
 
You also mentioned a Pro Channel "Bus", but the Pro Channel is essentially a group of VST Plugins that can be applied to an audio track or bus.  There may be meters visible depending on which modules are included at the time, but if the entire Pro Channel strip is disabled (at the top) it also has no effect on the track and bus levels/meters.
 

Your tracks may be quieter than others on Soundcloud because the other tracks have been mastered to optimise (or maximise) their true or apparent volume.

If you're not already using the appropriate tools to do the same, I suggest you do a bit of research into the use of limiters and compressors when mastering a track for distribution.

"The other level meters that I wasn't paying attention to, were lowering my output levels."
 
This statement shows me you still need to understand the signal path.
Meters don't lower your level. The level fader or knob is what controls your levels. The meter just shows you the results. There need only be a Master buss. All the others for your audio interface default to unity. If they are showing a low level then you are sending a low level output. As said over and over here, the master buss and the audio interface output channels should all show the same level unless you turn something down.
 Those other strips , metronome and preview mean nothing and have no bearing on your master unless you somehow have changed a default.
Where did you start the project from? Which template did you use? Or did you use a sample project? 

djwayne
Seriously, how many level meters do you have to have ?? ............. it's ridiculous.

 
Why - how many can I have=-)?

Well I tried mastering a track in Audition and my results came out way better....
 
http://www.soundclick.com/player/single_player.cfm?songid=13450555&q=hi&newref=1
 
.