Hi Abe,
Yeah...that's the theory, and technically it should be true. Many people have tried that method and prefer it...others prefer the way their music sounds via certain preamps. There are many reasons for that...some technical, and some emotional. It's true that most preamps are going to alter the signal to some extent, even if it is to a small degree, but some people do prefer the way the preamp alters their signal.
There are also many other issues involved. For instance...many CD players have built in volume controls on their variable outputs, but they are often rather cheap. They may do more damage to the sound than a good preamp will. Some people take care of that problem by using passive volume controls, passive preamps, or by purchasing a CD player with a good quality volume control. Other people try passive volume controls and preamps and decide that they prefer the sound of active preamps.
In the end, there really is no right or wrong way to approach it. Everyone has their own preferences, much like every other aspect of audio reproduction. Don't get bogged down by worrying about what is "best". It's much more fun if you worry about whether or not it sounds right to your ears (with your system...in your house). It makes a lot of sense to try the simplest, most economical solution first. If it sounds good to you, then you're done. Good luck!
Oh...by the way...
I hate to bring up another subject, but if you should make sure the output voltage of the Monarchy DAC is compatible with the input sensitivity of your Bryston amplifier. You can do this by checking with Bryston and asking them what their recommendations for minimum/maximum input voltage is (it might even be in your owner's manual). There is another thread listed today that concerns this very subject. If the DAC's output power is too high or too low for your amp, the music will either be way too loud or not loud enough. I figured I'd mention it...just to be safe and help you to avoid some future headaches.