I owned the Apollo for about 3 years. Never heard any brightness with it personally. Not that I doubt your ears/findings, just saying mine are/were different. I used a Bryston B60 and Audio Physic Yara Evolution Bookshelves with the Apollo. With that being said...
The DACs you mention are downgrades IMO. The V-DAC can't compete with the Apollo in any way. Then again, it's a $300 DAC compared to a $1k CDP, so it's really not fair to either component to compare them. Haven't heard the M-1, but Musical Fidelity's house sound is pretty far from Rega's IMO.
I haven't heard any of the rest of your system, so I can't speak of synergy nor what may be giving you some brightness. It may also be the room?
If you like what the Apollo is doing but want to take that up a level or two, the Rega DAC is a great choice. It does everything the Apollo does, only a great deal better to my ears. The only thing I had to adjust my ears to was the soundstage became a little more pushed back. It's bigger and deeper, but it's not as close. That may be a good thing in your system. In mine, it was just a change.
The Rega DAC sounds warmer and fuller than my Apollo did. In every way, to my ears the DAC is far better. The sound is on par with the Saturn. Not necessarily better than the Saturn, just a bit different. People have commented it sounds more along the lines of the Jupiter than the Saturn. Haven't heard the Jupiter in z very long time, and haven't heard the Saturn and DAC side by side to give an honest assessment of that statement.
To connect the Apollo to any DAC, UAE the coax (RCA) digital out. Toslink (aka optical) can sound very good if you're using a glass cable, but my experience with the Apollo told my ears that the coax out was a good bit better. That'll probably depend on the DAC as well. I didn't try my Apollo with the Rega DAC, but had auditioned several others (including the V-DAC) with it.
The DACs you mention are downgrades IMO. The V-DAC can't compete with the Apollo in any way. Then again, it's a $300 DAC compared to a $1k CDP, so it's really not fair to either component to compare them. Haven't heard the M-1, but Musical Fidelity's house sound is pretty far from Rega's IMO.
I haven't heard any of the rest of your system, so I can't speak of synergy nor what may be giving you some brightness. It may also be the room?
If you like what the Apollo is doing but want to take that up a level or two, the Rega DAC is a great choice. It does everything the Apollo does, only a great deal better to my ears. The only thing I had to adjust my ears to was the soundstage became a little more pushed back. It's bigger and deeper, but it's not as close. That may be a good thing in your system. In mine, it was just a change.
The Rega DAC sounds warmer and fuller than my Apollo did. In every way, to my ears the DAC is far better. The sound is on par with the Saturn. Not necessarily better than the Saturn, just a bit different. People have commented it sounds more along the lines of the Jupiter than the Saturn. Haven't heard the Jupiter in z very long time, and haven't heard the Saturn and DAC side by side to give an honest assessment of that statement.
To connect the Apollo to any DAC, UAE the coax (RCA) digital out. Toslink (aka optical) can sound very good if you're using a glass cable, but my experience with the Apollo told my ears that the coax out was a good bit better. That'll probably depend on the DAC as well. I didn't try my Apollo with the Rega DAC, but had auditioned several others (including the V-DAC) with it.