DTS plays 4db (at least) louder out of every receiver or processor in existence. Deal with it and turn Dolby up 4db or more to get equivalent volume. You may be interested to know that Dolby generally has more in the LFE channel, while DTS has the bass more spread throughout all 5.1 channels. And Dolby's LFE is generally louder, too.

The layer change will happen in no matter what audio you use, I'm not sure why you're blaming Dolby. Get a Denon 2200 ($600) or 2900 ($1000) if you hate layer changes.

Sounds like you have the dynamic compression mode turned on in your receiver. This is a feature of Dolby that I wish DTS would create, too. With most Dolby recordings you can turn on compression for late night viewing when you want dialog loud enough to hear, but explosions softer to not wake others up. Turn it off to get normal sound.