Preamp matching for Krell FPB amplifier

It seems to me that the obvious choice would a Krell preamplifier such as the KRC, KRC-HR, or the KRC-3. That being said I am sure that there are other manufacturers whose preamplifiers mate well this amplifier. The Krell amplifier is a pre Cast technology FPB. I was hoping to find out what current and previous owners have used and what kind of system integration was experienced.
Thank you for your assistance in this matter.

Audio Research Ref II mates VERY well with the Krells!
I run this setup with Thiel CS6 speakers and MIT cables. It is a very synergestic match.
I used to own the KRC 3 but sold it for the Sonic Frontiers Line 2SE preamp for my FPB 200. Their is something about the SF and Krell combo that just sounds right,as in toe tapping with a smile in you face thinking "Damn this sounds good!", excuse the analogy.
Source is EMC 1 MK II and speakers are Dynaudio Contour 3.0s
It probably depends somewhat on what sound you're looking for. Certainly one of the Krell preamps you mention would be an excellent choice if the Krell sound is one you like (I definitely do!). The other recommendations you have gotten are excellent as well, but will take the sound in a slightly different direction.

Krell has a reputation for unsurpassed bass performance but for being harsh or shrill on the top end. I didn't own any of the older Krell amps, but I own the FBP200c now and find it to be stellar on both ends of the frequency range. If anything, it's a little darker sounding rather than bright. For many, putting a tubed preamp in front of a Krell amp was a way of softening the sound, and people have had great success with this. The KRC3 had a reputation as being "different" sounding vs. the rest of the Krell line, meaning that it had a mellower sound. My point being, there are some that would say "Too much Krell!", and it might well have been with earlier Krell models, but the specific models you're talking about shouldn't have that problem. You've got one of those good choices in life where you really can't make a bad choice, you can only optimize your pleasure. -Kirk

If you are an FPB amp with no cast then the new Krell KAV preamp is perfect for that beast. It is esentialy the KCT without cast and paired with XLR cables you will get the most neutral and pure (unmolested) sound.
Krell is a lot better in designing poweramps than preamps. I'm just auditioning preamps with the FPB 600C, I prefer a preamp which keeps it's possible aggressiveness under control. I like the Pass X2.5, all natural sound colors and textures can be heard (btw. a lot better with the 600C than with the Pass X250). I also like the new Nagra PL-L, it has a nice and subtle tube sound and also keeps the highs under control, however the Pass lets me hear more good things of the original recording (the Nagra is not broken-in yet, so it might improve).
Have an option of getting a mint 2nd hand KRC for the same price as KAV 280p to go with a non-cast FPB.

Which do you think is a better option? The KRC used to be their top of the line preamp and the KAV is the current entry level - would technology have improved so much to make a previous top of the line preamp inferior to a present entry level one?
I use my system as Video & Audio and the Theta Casablanc II matches with my Krell 650M's perfecly. Very, Very, Detail, Open Soundstage, Excellent Mid and thunderous Lows.

I would suggest one of the excellent tube preamps from Consonance by OperaAudio or Power modules. You will have the best of all worlds!