Audio Research LS25 vs Pass X-1

Really, to make the LS25 sound it's best, it needs upgraded tubes in my experiences. Stock is just ok. The difference in the X1(which I've sold retail) is the basic difference between very good solid state pre's vs. good tube pre's. I'd call teh LS25 "good" higher end tube gear, and the X1 "better" modest high end SS gear. With different systems, you may have better results with one over the other. I like the LS25 with upgrades for your 100.2 amp.
I actually used to sell the 1.6's hooked up to the LS25 and 100 both. Sounded good. I liked the pass amp with he pass pre however...good chemistry.
Anyway, used to sell all of the above at one time. It's good gear.
A better tube pre however is the CAT stuff, no doubt. Used you can pick up in the $2k range. Good luck

check out audio video logic- they have the pass with the older power supply box(same inside) but identicle to the current version otherwise at about half off retail- can't beat that.

I had an ARC LS25 that I replaced with a Pass X1. The Pass had better dynamics and was just better all around -- more refined. Associated equipment: Pass X350, Levinson 37/360S (later an Electrocompaniet EMC1) and Dunlavy SC-IV/A's. The LS25MKII might give the Pass a better run for the money. Really, though, I don't think you could go wrong with either preamp.

I compared the LS25 MKII to the BAT VK-30SE and the Pass X-1. The BAT was not as dynamic as the LS25 MKII so right away it was eliminated from the audition (I owned the BAT at the time). The LS25 does not have a tube sound and the X-1 had a more laid back sound that seemed a little more refined. It also had better bass extension. I am going from long term memory here as it was a year or so ago.

Happy Listening.