My tracks loose quality after the Mixdown

I use Sonar and Reason via Rewire. Before the mixdown, the tracks coming from Reason sounds nice together with the tracks from Sonar.

After I bounce the Reason tracks and open it in a new track in Sonar, they still sounds great, but after the mixdown to a wave file they sound muffled, specially the drums.

I noticed that if I export the tracks from Reason, one by one, to individual midi files, and open each one in a new midi track in Sonar, and then bounce it, it sounds a little better, but it still sounds stifled.

You guys have any idea why, and what can I do, please.

Note: I export the Reason tracks at 24 bit. Then during the Sonar mixdown, I have tried it with 24 and 32 bits, but the result is the same muffled mixdown.

I don't know what dithering is, but i've tried with no dithering, triangular, power-3, and got no improvement.

thanks

This doesn't make sense.

You say you're exporting Midi tracks from Reason, but then go on about bit depths, which Midi doesn't even care about.

Perhaps I'm not reading it correctly, please correct me if I'm wrong, but as I said, it doesn't make sense.

I doing the same guess as Beagle, while mixing you are not routing tracks through the same exit as mixdown does.

Stereotracks suddenly mono is what your description makes me believe is happening.