Preamp for Krell KAV-250a amplifier

Since you like Krell, try the KCT. Rowland also sounds good with Krell (but different). A Hovland 100, Aesthetix or a CAT Ultimate may do the trick if you're into fast, dynamic & clear tubes. Ayre, Klyne and the bigger Sims should also pair well (I'm not sure about the impedance matching there).
Don't know the A-Illusions.

Pray, what's the budget & what are you looking for in terms of "sound" -- a clue or two :)?

Thanks Gregm. $2000.00 used would be about my budget. I like my sound very crisp, very detailed, very sharp. Hope it helps.

Used: Krell, small Goldmund, old Rowland (consummate /consonance?), Pass of "Aleph" times, maybe a smaller Klyne... or even a 2channel Adcom ("750", I think). Try to set aside ~200 for used IC (if you don't already have a set that's fast). Cheers