Anyone experienced the Luxman MQ-300 or/and The Air Tight ATM-300R?

H_bomb,
Your current amplifier is a 25 watt push pull circuit. So probably about 4 or 5 db more than the 8 watt MQ-300. If you’re listening at your typical SPLs with the volume control (VC) at the 9 o’clock position it suggests that there’re is excessive gain in your system. You would want to utilize much more range with the VC.

Interesting the 8 watt MQ-300 is nearly double the weight of the MQ 88C!! This certainly tells you something about the size (And presumably quality) of the transformers and power supply section. As I noted yesterday the Luxman MQ-300 seems to be an all out effort premium tier  SET amplifier. 

What are your typical listening levels in your 14 x 16 ft Room? You have nothing to lose with an audition with your speakers. This would settle the matter one way or the other. 
Charles

Hi.I listen at low to medium volume.

Well, given your listening levels and room size who knows? The pairing could ’possibly’ meet your needs/expectations. . It will be interesting to see how your current Luxman compares to the MQ-300 and or the AirTight SETs.
Charles

Yes. I love the system I have right now. I used to be all shindo amp/pre and switched recently.

For a speaker with as low sensitivity as the Devore Super 9, you might want to look at the Art Audio Elise.  It is 16w (double that of the Luxman or Air Tight) and uses a 520B which is a 300B derivative from Emission Labs and very similar to the old KR VV 52B.  

It is a wonderful sounding amp with lush mids and better bass than you could expect from a SET.  This unit replaced the Jota in the Art Audio lineup and is the amp in my profile photo.  

A 520B based unit will be much closer to the sound profile of a 300B than an 845 or 211 will be.  The other option would be to look at a 300B parallel SET like the Art Audio Argento but then you are running four 300Bs which can be brutally expensive to maintain longer term.  

I am sure there are other 520B based units or other 300B parallel SETs which may solve your issue.  I just don't know them off hand.  

Full disclosure, I am the importer for Art Audio. I am pointing these units out because they solve the marginal challenge you are facing in terms of power.  We have plenty of 3rd party review of our amps at a variety of sites.  

Good luck!