Krell FBP200C/which tube pre will sound best

I have a Krell 200C and want to make a jump to tubes in the pre-amp to smooth out the sound. My speakers are B&W-802. Shunyata sidewinder gold power cords, wireworld ecilpse 2 speaker cable. Krell KAV-250 cd. My only concern is I hear alot about upkeep. Need some imput. I listen to jazz, classical music, thanks in advance for any guidance you can offer.
Be careful!

I have the FBP300 that just came back from Krell with a LOT of repairs having to be done.
They told me that they feel that the person that I bought it from, probably hooked it up to an inferior tube amp.
I would clear it with Krell before I made that move.

I have the FPB mated with the KRC-HR driving big B&W speakers. ... A match made in heaven!

I am using CAT Ultimate Preamp with my Krell 600C driving the same speakers you have the B&W802N. The dealer who I bought the Krell from measured my CAT preamp after it warms up and found that it has a very low DC offset which is acceptable to be used with the FBP amps. Krell stresses that if the FBP amps are to be used with and tube preamp that has high DC offset, the amps needs to be reconfigured internally. The synergy of CAT with the Krell is very very good. I am going to hear the KCT with my amp soon, which will be using the CAST connection... I will let you know how it sounds...
I am using a Krell FPB 200 with a AE-3 tube line level pre-amp. There is a section in the Krell User’s Manual which will explain the use of Tube Equipment with their amps. An internal jumper/switch needs to be changed in the amp before use with tube equipment. I called Krell told them what I wanted to do and they faxed me the instructions. The instructions are easy to follow and it only took 5 minutes. I have not had any problems and am very happy with the combination of tubes and SS equipment.
I am on and off with solid state preamps but I had no luck with them. I'm staying with a Sonic Frontiers Line 3 with my Krell FBP200C. If you want to use a tube preamp with your 200C, you'll have to contact Krell and they'll send you instructions. They sent me the instructions and it took me about 5 minutes to get it done. My system is sounding great now.
I get the sense that the SF Line preamps may be one of the few tube preamps that can be used safely with the Krell FBP series without having to use the internal jumpers that insert coupling capacitors into the signal path. The Line series preamps feature a direct coupled output -- and no coupling capacitors. According to my FPB300 manual, the jumpers only need to be utilized with capacitively coupled tube preamplifiers. The FPB300 is a new addition to my system, and is now pared with a SF Line 3. I do plan to touch base with Krell on Monday to see is my understanding is correct.
I am currently using a CAT ultimate with Krell FBP 300 driving B&W N802. This Pre and AMP Combo sounded fantastic to me. I use NBS Monitor I cable with one end RCA and the other end XLR specially prepare by NBS.
I just purchased a pair of 250fpb mono's & I asked about this very issue. My dealer said that the Sonic Frontiers Line 3 I am using would not be a problem for my amps. This dealer sold S.F. gear at one time. If anybody hears differently please let me know. Lwin
I have been using a Sonic Frontiers Line 3 with my KSA200s and it's a wonderful combination. Highly recommended. SF Line 3s are going for around $2-2.5K used right now. A great buy. Its nice to use balanced between the two which most pre's don't allow.