Opinions please - Rowland 625 S2 vs Luxman M900u ?

Dave here’s what I think FWIW. I absolutely would keep that Luxman combo intact. I do not think that the 625s2 is a superior move. I personally had no ‘weight’ issues with the Luxman and would hate to give up their all around superior attributes. If you really want more weight you could pick up a used Shunyata or two which will definitely add weight. I hate to see you count on a power cord though. Here’s a grand thought. Your C-900u has excellent tone controls. Give the bass a slight bump if you want a meatier sound. It’s probably not what you want to hear but that Luxman amp is special.
BTW I never seem to take my own advice. What cables do you use?

@4425 great thoughts; I will play around with some power cables; I have some mediocre Wire World stuff but a good friend has shipped me some stuff from Nordost, Audience, and IsoTek; I think it arrives today;

The speaker cables are Transparent Audio Super Speaker Gen5;

I do use and LOVE the C-900 tone controls; Can't live without, lol;

I hear you 100% on not heeding one's own advice;
The M-900 has some super incredible traits and if I could flush out some fullness and power drive in the lower area, I would hit the brakes full on.

Hey Dave, for what you are looking to accomplish with your system and way you like it, if you are looking at power cords, try Triode Wire Labs Obsession NCF power cords. You will be surprised. In the grand scheme of things, they are not terribly expensive either. You will thank me later ;-)

one thing dave that i can tell you from experience in house. the shunyata Alpha NR is definitely ripe/full  in the bass region. still i would think that the bass tone control should get it done. i think it’s centered at 100hz which is perfect for fullness. 

Some food for thought....

https://www.soundstagehifi.com/index.php/equipment-reviews/838-luxman-m-900u-stereo-mono-amplifier