How much do I need to spend to get a preamp that sounds better than no preamp?

Most everyone knows that the McCormack amps have high enough input gain that allow passive preamps to drive this amp and as a result sound spectacular.

I am familiar with your Audible illusions L1 preamp and I liked it a great deal. It was said to be the same linestage used in their more expensive model the Audible Illusions 3 which may be debatable however It may not be to your liking nor the ideal companion for your McCormack DNA-1. Several years ago when I owned a DNA-1 with a Revision A the best sounding tube preamp to my ears was the VTL 2.5, and everybody else in the household that had a high appreciation for great sound agreed.

I think it is worth mentioning that the OP's Audible Illusions L-1 preamp has a gain control and a master volume control. So one can set the perfect amount of gain for the amp and then use the master volume control there after.

Keep in mind, there are no right or wrong solutions here but rather what the Op likes. We could give scientific measurements from now on (don't think for a minute they are not appreciated) but you already know it really comes down to what the OP perceives as the best sound, at least to his ears. Apparently he likes the dynamics of an active preamp ( like his L1) but again I would consider the McCormack passive preamps as an alternative for greater dynamics.

The audible Illusions L1 offers a really good sound for the price and for some reason much of the competition in its price range don't come close. Yes they can be a bit hard on tubes. When I had mine I ran the same tubes for two years without failure but most of you know that many of the NOS tubes are not durable enough to last without premature failure. So it really comes down to using durable tubes or at least what is recommended by the mfg. Another thing to consider is that even though you might turn the power off the tubes are still lite at a lower voltage .

I forgot to mention that when you purchase an Axiom passive preamp the mfg will ask you what power amp you will be driving so that it can be configured to deliver the best sound. When you buy a used one on the internet it may be designed for a different amplifier and you might not experience the best possibble sound and dynamics you would expect. Just a thought.

Honashagen, With the L1, initially you need to set the gain control half way up (12 o clock) as recommended by the mfg and go from there. Also if you want to increase dynamics, the McCormack is not that bass heavy, certainly not Krell-like. You have two pairs of outputs on the L1, why not use one pair for an active subwoofer, just make sure it is a musical sub with tight and tuneful bass.

You mentioned components you used to own like the Crown and how you remembered you liked the presentation a lot. Let me say this, each and every time I revisited older components that I used to be fond of, I left disappointed and it turned out that what I currently have was superior. If you were to sell the upgraded McCormack and AI preamp there would be an over wehlming response from buyers as these two components are not seen for sale lately.