Best preamp for my Krell FPB 600

Just looked at your system very cool! I concur with the above always trust your ears. And regarding your cd player I had a KPS20i back in the day, I remember it being very detailed and a nice match for my then overly warm system. I ditched it cause it couldn't read most CD-R's, these days I have hundreds of them if I ever need a coaster lol. Have fun and happy listening!

The ML 38S is an excellent preamp and will sound fine in ANY system!

The ML 38S is an excellent preamp and will sound fine in ANY system!

See, I cannot agree with this statement.
That is where synergy and subjectivity come into play.
Personally, I owned the ML 38S for a few weeks (over a decade ago), and I did not care for it at all. However, the gent that I bought it from loved it, and the gent that I sold it to loved it. So I would never say that it was bad gear, it just didn't suit my system/tastes at that point in time.

So it's all about system synergy and personal tastes. That is why I told the OP to just enjoy what he has if it sounds good to him. 
I did not mention my poor experience with the 38S, because that is irrelevant.

From my experiences, ALL gear can sound great with the right ancillary equipment. There is no one piece that sounds great with everything, just as there is no one piece that sounds terrible with everything.
It's all subjective, and system dependent.

Cheers,
John

+1 @jmcgrogan2 synergy is everything!

I have a couple of Krell EV 600's. Love their sound and strength. I like a tube preamp, although no matter how much u spend, at least in my experience, you're always going to have "tube rush."  When my system is "at rest" my Aesthetix Signature preamp puts out around 5 db of sound over what is heard when muted. From my experience, your power amp will merely amplify what's being put in to it.  If you're in to classical music, or anything with a lot of very quiet passages, u may want a SS preamp. I just installed some RCA quad matched 12ax7's low noise tubes I bought from Vintage Tubes and still have a somewhat significant noise floor, but can only be heard when music isn't playing. It depends on your particular taste. To me, tube preamps, have more of a fuller and buttery sound.