ARC D400 vs D400 MkII

Ok, so last year I was on the hunt for a solid state ARC amp to pair with my LS25 MkII linestage. Solid state designs from ARC seem to have been sparse over the last couple decades, to say the least; I’d read online that the D400 MkII is “the one to have”. 
 

Well, I ended up with a one-owner original D400, thinking that I’d use it until I could unearth a MkII at a later date; the price was very reasonable , and I figured I could resell it at no financial loss at such time as I found a suitable replacement.

Now I’m wondering if proceeding with my original plan is worth the hassle and uncertainty of exchanging a (in terms of operating condition/reliability) known quantity for an unknown quantity.

I know this is a shot in the dark, but I was hoping someone Agon might have had a chance to listen to both versions of this amp and elucidate how much of an improvement the MkII version is, and in what capacity.
 

thx