benjosepf1,
I'd suggest you audition the M700s in your room and system. I think you'll find that the M700s are a very good match with your Rogue 99 tube preamp if you like the sonic qualities of this preamp.
The main characteristics you'll likely notice on the class D mono-blocks is that they have a very low noise floor, very low distortion levels and that they're very neutral. They are like the audio ideal of a straight wire with gain meaning nothing is added or subtracted from the inputted signal. This will result in the combination of the sonic qualities of your source components, the recordings and the Rogue 99 tubed preamp the main determinants of your system's overall sound, since the M700s will just be faithfully amplifying this combination's output without any added sound quality of its own.
You should be aware that class D amps are very accurate and revealing which can sound very good if the quality of your recordings and other components in your system are of high quality. However, if the quality of your recordings and other components in your system have deficiencies, class D amps will not sugar coat anything and you will be clearly aware of any deficiencies.
The downside of using class D amps is that the quality of some of your music , that sounded good to you through your previous amp, will not sound equally as good if it wasn't well recorded because the accuracy and transparency of a good class D amp will expose that deficiency. I use a pair of D-Sonic M3-600-M class D mono-blocks in my system and, fortunately, only my Coldplay albums were exposed as poorly recorded.
The flipside of this, using class D amps with well recorded music, will be sound quality performance levels that are exceptionally good. Music emerges from a dead quiet background with live-music-like dynamics and a very detailed presentation that still sounds smooth, organic and natural.
I suggest you give the M700s an audition and experience good class D performance and decide for yourself if you like the overall sound quality in your system. I definitely advise doing so before buying anything else to ensure you make an informed decision.
Enjoy
Tim
