Pass X-250.5 or Plinius SA-103

Coming from a biased Plinius SA-102 owner, I'd definitely go with the class A warmth and smoothness of the SA-103... and your speakers are efficient and would not benefit from the extra power of the Pass X-250.5.

Other nice advantages with the SA-103...
A. Toggle mute / standby switch
B. Toggle option of running in class A or class A/B
C. It's "Green"... only draws 40 WPC in standby mode
D. Smaller footprint than the Pass X-250.5

I've never had a problem with my SA-102 in two years of ownership... not even a blown fuse.

If money is an issue, I am downsizing and going back to the Pass Labs Aleph series. Still great amps with many models to choose from. I have been running one Aleph 3 with my Audio Physic Virgo IIs with great results (30w into 8ohms,60 into 4ohms). I have another one the way so I will be verticlly bi-amping for extra headroom. My Virgos are a tougher load than your Nines...4ohms at 90db. I am downsizing but got a chance to hear a Pass X-0.2 in my system and put my X-1 up for sale (big upgrade). My favorite the Aleph 2 is for sale on Audiogon....I do not know the seller! They are not the biggest mono blocks in the Aleph line but very sweet!

Does the Aleph 3 have balanced or single ended only?

The Aleph 3 is single ended. I think the other Alephs were single ended or balanced (with the exception of the 0s ?)