More watts or better power ?

Russ, I agree and that was my initial thought process. Does it make sense to go with more watts, having a system that sounds good now. Could I really take it to the next level with a bigger amp? Based on comments here, and my own thoughts, probably not cost effective. Like you said, the change would have to be big and it's not worth the $ at this point. I'll look at protecting my gear with isolation and conditioning. 
   PS, I sold my Parasound A21 to a friend and he's running it with a pair of Spatial Labs M3s. It sounds great, great amp. 

How about better speaker placement/room enhancement?

You're realistically only using single digit wattage, nowhere near the amp specs.

I think this article will be helpful.  Certainly relevant to your discussion title.  
https://www.primaluna-usa.com/less-power-more-bass

If you in fact need to do anything at all, consider power quality over more wattage.

Tablejockey's comment is on the money.  I just did the experiment outlined in the article with a 35 watt amp driving 86 db sensitivity speakers.  Only takes 4 watts to arrive at a 92 db level. As it turns out, for me, 92 db constant white noise at 1 meter is WAAAY louder than how I listen even given my listening position is 3-4 meters (not 1) from the speakers.  

Mark, you don't need more watts, unless you notice a lack of low-end at your typical listening level. That's a sweet amp that produces high current which is what you really want in your system.

The only addition I would recommend is power conditioning/surge protection. You'll get lots of recommendations here, so you should state your budget. Only sources should go into a conditioner, since most are current-limiting. That means a high-current amp like yours can lose dynamics due to the filtering used to lower RFI/EMI and noise from the mains. The result of power conditioning is a lower noise-floor which will reveal more detail, better imaging, and air around instruments.
Anyway, a Pass Labs amp does not need a PC, it is designed to reject common noise.

Based on Stereophile measurements of the XA25, I would say that the amp is good for up to 30 watts per channel clean.  Anything above that will start to have distortion/clipping problems (not that you would really notice any difference between 25 and 30 watts, lol).

That being said, it takes a very beefy power supply and large heatsinks to run a stereo amp at 25 watts per channel "full Class A".  That amp is going to have extremely clean and full sound.  This Pass XA25 has a nice mellow full sound.  Very nice to listen to, but it is somewhat laid back when compared to more dynamic amps.

The BHK 250 will likely be able to give you slightly stronger deep bass strength, with it being a 250 watt per channel Class AB amp with good size power supplies.  The BHK is a cleaner and more neutral sounding amp than the Pass XA25, but it is still mild sounding (most likely due to the stock Genelex Gold Lion tubes).  It's likely that you can get this amp to sound more exciting with PSVANE or Electro-Harmonix input tubes.

I'm not sure that you would really notice or care about the slight increase in deep bass strength, since it's a 6" bookshelf speaker, but I could be wrong.  Going from XA25 to BHK 250 is really about a sonic signature change.