Tweaking preamp and amp combination

I have an Audio Research Sp9 MKII preamp along with McCormack DNA 125 amp upgraded to SE+ in 2015. I have Vandy 3A sigs with a pair of 2w subs. I am looking for options on replacing or upgrading current power amp. Below is a list of considerations and looking for recommendations on best option to compliment my current system.
  
  1. SMC Audio upgrade of the DNA 125
  2. Purchase used Audio Research D200 or D300 power amp
  3. Other options that would compliment the 3A Sigs and sub combination