Which would you choose?

I wouldn't go with a vintage preamp. I had the Krell in my system for a while and I've owned the Pass and neither was all that great when they were current, let alone what you can get for a more modern preamp used. You can make a case for a vintage amp, especially tube, but I was never impressed with vintage preamps.

If you absolutely must go with a vintage SS preamp, I think Rowland and Levinson preamps from that era are much better.

If those were my only two choices, I would lean towards the X-02.

Though I somewhat agree with Zd542, you can do better than either. I've always preferred a tube preamp, but if you require SS, Klyne is the best I've heard, and what I would look for. Rowland, Threshold and Classe also made decent preamps, though I found Levinson to be the worst of the bunch in my system.

I too spent plenty of time with each and didn't like them either. I ended up with a Quicksilver preamp and loved it after an MIT rewire. I think that technology has come way too far. The ML,while better than both was still a bit dark compared to good pre amps of today. What is the budget? Can you afford a used Ayre pre amp? I know the Audible Illusions is a great pre for the money if you're willing to do tubes (not sure how it mates with you amp though). I've yet to hear a SS better the Ayre....even the tube stuff usually isn't better unless you are into the esoteric stuff, but I'd want to hear it in my system first. Good luck.

Could just buy a modded PAS-3 , still sounds better than most preamps.

I always like Krell pre-amps when I hear them. VEry dynamic lively, clean, transparent.

Have not heard Pass but would expect excellent results there as well, though some difference (warmer sounding perhaps?) than Krell.

For a vintage system like that, I would go in thinking Krell would add some very nice ingredients into the mix and help work towards a more neutral sound. Pass might as well, but less familiar to me.