McCormack DNA 125

@highend64 stock DNA-125 is an excellent amplifier. If you want to mod it I would the just wait for a modified version to come up on used market. Don’t buy this amp to get it modified…that’s going to be money never recouped. 

@slaw honestly not on a lookout for one so can’t say. To share my experience…

At the time I owned B&W N803 driven by a DNA0.5. Upgraded to DNA-125, loved it so much and needed slightly more juice for the N803s, I sold the 125 and picked up a mint DNA-225. That amp was everything I was looking for, sound and power wise. Just totally gelled with then rest of my gear (ARC LS-15, ARC CD-3MkII). But the upgrade bug bit. I sent the 225 in for the Gold Revision. When I got it back it sounded pretty much like a different amp. Long story slim, the synergy was no longer there even after the extensive break in (300+ hrs). It just didn’t work out for me. The sound was fatiguing with heavy presence region. I actually preferred the sonics of the stock 125 over the modded 225. I ended up selling the 225 and in the process took a decent hit. The market at the time (2006) was flooded with modified McCormack amps. I saw my amp on the market few more times shortly after, changing hands.
I ended up picking up a mint Pass X250.5 locally and was back in the listening chair with a smile on my face.

So what I’m trying to say here is if one is looking for 125 to mod, go straight to 225 and just enjoy the music because that amp is truly special. Don’t bother with mods. CJ did a super fine job with DNA series amps. The 225 just makes music…bottom line. The stock 225 is one of the components in my audio journey I regret getting rid of. It was that good.

Now, YMMV and I won’t argue. Just sharing my experience.

@soix Synergy was the first aspect I talked about it just didn’t make to the snippet you used here. But regardless…
Think about this…the stock 0.5, 125 and 225 sounded amazing, the X250.5 fit right in. However the modded 225 didn’t gel with the rest of my gear, my room and my ears. You can definitely stick to your guns and call the smc mods an improvement.
I call the modded amp colored, no longer neutral, and with a hump in the presence region that was very fatiguing. It didn’t show anymore of the character of my speakers or any other component. There’s no reason to screw around with a perfectly seasoned dish. But that’s what those mods did. 
There may be systems and listeners that can benefit from this type of sonic change, without a doubt.

I still consider DNA-225 in its stock form to be one the best amps I ever owned though. Totally loved it.