Since Krell 302e & Cary SPL-05 have (gain/imp issues) what tube pre is best w/ the krell?

I would actually look at the Krell 202 or 222 preamps (even an older Krell KAV-280p is nice, but doesn't have the power supply of the 202/22).  The Krell's bipolar Class A gain circuits give you a nice sweet sound but still have the slam/punch/immediacy.  I would avoid the Krell Phantom preamp as I think they are overpriced and there's nothing much in them (even KAV-280p is better in my opinion).

You could look at some of the Pass Labs preamps.  They are Class A and use JFET/MOSFET gain circuits instead of bipolar.  This may give you more of a richness in the sound (not that Krell would be lacking warmth), but keep in mind that not all FET circuits are created equal.  I have not heard Pass Labs, so I could not comment.

Eric is a fan of Ayre, but I have no idea what that sounds like.

@4425 - well, I probably should have been more concise.  When I say "Krell Phantom", most of the time I am seeing Krell Phantom III preamps.  This particular model may sound good, but I think it's somewhat trim on the internals:

http://i.ebayimg.com/00/s/MTA2MFgxNjAw/z/~v8AAOSw~bFWHBzD/$_1.JPG

I suppose it's not too terribly expensive, but at $3k+, I might think it's worth it to bite the bullet for a 222.  The Krell Phantom (with separate power supply) and Phantom II preamps look really good, but they are also expensive (akin to the 222/202 models).

If your looking for bass slam, make sure you get a really beefy power supply.  It's been my experience that the Krells with smaller power supplies can be somewhat light on bass (and more forward in the mids/highs).