scook
When exporting did you try using Master Bus only in the export settings?
Are you exporting a wave?
 

1 . No i have not tried master BUSS only with the export ( i have all settings default ) because it have always worked in X3
so why should it not do so in Platinum !
2.  Yes wavefile only

listen
Voxengo Recorder what does it do for the mix "sound wise" just curious - I use Voxengo products I'll have to check out the recorder...

Voxengo recorder is an vst plugin ( 32bit only ), you can put on any Audiotrack
and record from it ( that track / buss ) and to a wavefile to your HD.
It don't do anything to the sound ... rather than recording in realtime from the selected track or BUSS.

Start playback on sonar, hit record button on the Voxengo recorder... viola it records to a wavefile 

You might want to try freezing each of the synths.  Perhaps one of them behaves differently when exporting vs realtime playing?  If you freeze them you should get the same as they would produce on an export.  Might be able to narrow it down.  But if it is Sonar, it's not reproducing here and no one else has reported this.  Going to be hard to get a fix if you are the only one with the problem.

Just listened to the examples.
This is not dithering.
This is Sonar exporting from a different place from what you think. Can you post a screen shot of your export dialog?

Did some adjustments, now the arp is messed up totally
but when i play it in sonar all is good.

Used the above settings when i did the export...

orginal sound in sonar is like the one from voxengo recorder ..

Beats me what happens, i have no clue at all

EDIT: Sound Examples deleted

Too bad i need to use the plugin to export the audio, when sonar can't
but it is a solution...

Soundblend
Ok i downloaded Voxengo recorder an put it on my Master BUSS, hit play in sonar and recorded the master

The sound of the recorded file with ( voxengo recorder ) is exactly what i hear in my DAW ;-)

1. Sonar Mixdown ( boomy and not that good sound )
2. Voxengo recorder ( exactly as i hear it in my daw )

there's no change in EQ or other..., just different way to mixdown

Now tell me what's wrong ?
 

I just had a listen ...
 
this could be a very common problem: when a bass starts sounding thin, there are often phase issues (signal gets thinner due to canceling when summing similar signals with a short time delay) ... but here it might be working just the opposite way
 
here's what I think ...
 
#2 with the voxengo (your supposedly better version) the arp sounds "phasy" and thus thinner ... so either you have a phase/flanging FX on the arp that for whatever reason is not active when export from Sonar ... or what I actually suspect, you have some unintended phase issues happening like the synth being routed to 2 tracks with one requiring different processing buffer (=latency) than the other track ... so when listening in real-time you hear this "phasy" thinner arp (due signal cancelling) but when exporting tracks get properly aligned and thus sum up and get much louder ...
 
try the following and see if it helps ...
 + disable all direct monitoring
 + if using outboard gear or external synths, record/bounce them to audio tracks
 + try freezing all FX that relates to the synth ...
 
then try exporting again ... I'm sure if you properly transfer your MIDI to audio (freeze/bounce tracks) before export, there will not be any difference between a direct export from Sonar and a plug-in in the master bus ...
 
 

PS: header changed to suit the issue

I have actually tried BUSS only export without Reverb and FX, thats just sounds horrible

But ill do it again and also show the export option, just to prove my point

Anyone can feel free to get the project file... to test it out ( it contains no audio ) so its got small size

@ Vastman : telling this to me :
" This does not seem to be a bug, although you're obviously "bugged"  "

That's just child'ish, when i got a real problem to solve, not acting like children on steroids
but some may not understand ?, even if they get it in with a tea spoon ! 
I am not here to offend, but seriously ... i need to respond sometimes.

Back to my issue :

* forget dithering, it has minor to no effect, i have said it several times, sure someone agree
* All instruments are VSTi's
* no automation
* no chorus or flanger
* no phase issues

All VSTi's are directly routed to the MASTER BUSS

VSTi's used are :

1. SI bass guitar
2. Ample Guitar M II
3. Addictive Drums 2
4. SynthMaster 2.7 Player

BUSS(es ) :

1. metronome =  ( muted )
2. Preview BUSS = for loops playback ( muted )
3. Delay bus with Karlette delay ( Active )
4. Reverb BUSS with Lexicon MPX reverb ( Active )

Routed to MASTER BUSS.

other than that some Prochannel EQ , Console, rematrix reverb

FX chain, with Klanghelm MJUC, and Code red free

That covers more or less the FX's

Ill do  again as suggested with BUSS export and only master and untick everything
ill post a Export dialog again also an new Audio example with the Woxengo ( as i hear the sound in sonar )
and the Cakewalk Mixdown once more

Atm, i need to go out for a short time but ill come back to it.. 

Bristol_Jonesey
1 - Switch your export Source Category to Main Outs
2 - Export at 32 bit with NO DITHERING
3 - Import it back into Sonar on a new track
4 - Route this new track directly to your interface, bypassing the Sonar busses
5 - Invert the phase of the export. When you hit play, you should hear nothing.

Ok heres what i did :



1. Exported Main outs audio 32 bit wave, with no dither
2. opened new project and made 2 Audio tracks
3. first track is in normal mode ( no phase flip ) Green track
4. imported the same wave file into track 2 ( hit the phase flip button ) red track
5. Routed the audio directly to my interface

No sound on busse's ..

Hit play : And as you said i hear no sound ( complete silence )

if i mute 1 of the track's i will hear sound

Conclusion no phase issues



http://postimg.org/image/nvmkwo74d/

BTW, I'm still suspecting phase issues and you are mixing against it without noticing until the export ...
 
There are 2 prime suspects: AD2 (which has a phase problem if used with parallel compression and tracks not frozen) and your delay bus (check and post your delay times in ms ... if it's a multiple delay VST it's easy to have one of them set really short without noticing) ...
 

Certainly seems to have fixed the issue :-)