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