Synergy between AR Ref 3 and Pass X amps

I am concerned about the compatibility of AR Ref 3 into Pass x-1000. The x-1000 has a low input resistance of 20kohm and have read that Ref 3 prefers amps with higher resistances. Any advice or experience?
I tried a Ref3 with XA-60.5, which have input impedance a bit higher than 20k ohms. The match was OK, but overall the sound was flat and uninspiring. I was unimpressed with the Ref3/XA-60.5 combo.

IMO, you want a preamp with output impedance under 200 ohms to mate with the 20k ohm Pass X-1000.
Similarly, I was wondering how an ARC Ref 3 (output impedence 600 ohms balanced) would match with a Mac MC402 (input impedance 20,000 ohms balanced). But I imagine I would encounter similar difficulties as Tvad. I am currently using a BAT VK-31 SE (output impedence 300 ohms) with good results but the prices on the Ref 3 have come down considerably in anticipation of the Ref 5.
No issue with the impednace match. There have been numerous threads discussing about this topic. I have an LS-25 Mk I and X350.5. There are no issues. My friend is using Ref 3 with X350.5 without any issue.

My concern with your combo is that Ref 3 is fairly neutral, and the X1000 (non .5 version) is also very neutral. You may or may not like the end result. (Or the result may not be what you would expect.) I had compared the X350 and X350.5 side-by-side, and the differences are not subtle.

I have tried my Ref 3 with Pass X-250, 350 and 350.5 - no problems at all (other than mentioned by Gundam91).
Thank you for all your responses. Looks like I should either go with the AR110/210 or switch to Pass completely. Any advice on that in terms of sound?
Gundam91, I almost hate to ask, but what differences did you hear between the X350 and x.5 amps?
I've run the Ref3 with X-600 monoblocs and it sounds wonderful..I have no experience with the X-1000 monos.
I am going to try to answer several questions all at once. These two tests were conducted at least 2 to 3 years ago. I had heard the X350 and X350.5 compared side-by-side. The speakers were some big Avalons. Front end was a Sony SCD-1 feeding into a Sonic Frontier DAC 3, then into a ARC Ref 2 mk I.

The X350 sounded sterile in that system, had the very typical SS sound that people gripe about. Whem comparing to the X.5, the differences become more prominent. The X.5 had a warmer midrange, but at the same time better rendition of the bass, also deeper. More air on the top, but doesn't not feel so edgy. All the panelists was surprised at the amount of differences we had heard. We thought the differences merits more than a .5 upgrade status.

Some time later, we did a comparison between ARC Ref 2 Mk I and Pass X0.2 with the same set of panelists. At this time, my friend had kept the X350.5 and sent the X350 home. He had these two preamps for a while, so he was deciding which one to let go. We went back and forth. The X0.2 actually had a warmer, more tube like sound than the Ref 2. The Ref 2 was more extended at both ends. (Shouldn't it be the other way around?)

At the end, the Ref 2 won by a slight margin. I was able to convince the others that the Pass remote just sucks. I am fairly quick learner with gadgets, but I cannot figure out how to use the damn remote. Second, I think with a set of good NOS tubes, the Ref 2 would outshine X0.2 in the midrange department. So at the end the Ref 2 Mk I won based on "potential". But we could live with either happily.

On a different note, again focusing on the X-1000, I had a chance to do an A/B of the X-1000 vs Krell Evo 1 fed through a krell evo 2 (non-cast on both to keep it fair). The Krell was better mainly on its ability to project images with greater solidity around it. You could literally feel not just hear the wind instruments. Otherwise, the x-1000 were not too far behind, maybe even with better bass impact. But 3D imaging was well behind the krell.
I had the X0.2 preamp in my system for a short period, the Ref3 totally outclassed it in my system. I was using Pass X-600 amps with both preamps.
Ahh, but have you tried the new Pass Labs Preamp XP-10 or XP-20 with the Pass Labs X 350.5 Amp ?
Oz, I'm all set for now.....I love the Ref3 and I just don't have the bucks to consider auditioning the newer Pass stuff. Sure, I'd love to hear the X-600.5 amps...not so sure about the newer Pass preamps...the next preamp I buy will be the Audio Research Ref5......amazingly, I just can't imagine anything being better than the Ref3, just an amazing sounding preamp.
Amongst solid state amps, any recommendations on what i should audition that would go with the ref 3s?

As stated, the comparison was done a few years back. Two of my close friends currently own the Ref 3, another one had it for a brief period and didn't like it a bit. I don't have the kind of disposable income like they do, so I can only upgrade once every so often, like 6 or 7 years at a minimum. And go listen to new gears at their houses whenever they felt the itch to upgrade.

Like I said, I could be happy with either. I am sure the new Pass preamp would sound sweet. And it would be interesting to pit them against the Ref 3 or the soon-to-come-out Ref 5. But maybe when I win that big jack pot someday, I can try new toys every year. ;-P

For now, my GNSC modified LS-25 Mk I + Pass X350.5 will have to do....My next big investment is to build a dedicated room. It's in the works as I'm writing this.