More watts or better power ?

Check the Stereophile review of the XA25 to see how many watts it can really put out (in AB).  Given your speakers, the size of your room, and your volume levels, it is more than sufficient.  Plus, at least some owners familiar with PASS gear would pick the XA25 as the sweetest of all his amps.

I'm really not sure what itch it is you're trying to scratch.  A current deficiency in the system?  Just the need to try something new?

Adding a Puritan PSM 156 to my system made an audible improvement (unlike many other power conditioners).

If you just want to experiment, how about some Silversmith Fidelium speaker cables?

"...Russ, I’m not saying my system is lacking and being held back, just curious about peoples thoughts on more head room vs cleaner power. The XA25 is rated at 50wpc at 4 ohms, which the Amators are. The amp is class A / AB and weighs about 50 pounds. It’s pretty beefy for a 25 watt amp..."

I believe the Pass amp is a fine unit and that even at 25wpc is producing enough power, if you are happy with it’s output. What a beefy power amp does for you is mostly in the frequency extremes. A big power amp adds weight to the music, even at low volumes, that’s what they do best. It would be a solid move up. I’m not suggesting that you are in need of more power but you are in need of the sonic change a powerful amp can supply. My LS50s sound way better with the Parasound A21 than they do with my little tube integrated and I don’t play loud. The other change you can make is better loudspeakers, that will also get you in the right direction.

P.S. You have a fine system so you'll need a big change to advance it to the next level, just saying. 

Thanks Twoleftears, as I said, my system sounds very good. I was just wondering, in my system, if upgrading to a higher watt amp could make a noticeable difference. Or at that cost, would I look at line conditioning as a similar upgrade instead? 

Regarding speaker cables, I assume that speaker cables have a lesser effect on sound quality than interconnects. And because I have to run my speaker cables down into the basement and then up on the other side of the room (20' - 25') I have not invested in high end speaker cables. If I put my amp near the speakers then I would need 20'-25' interconnects, which does not seem a better solution. 

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.