surprising comparison of tube preamps

Hi and thanks for your help. I have been using an ARC LS25 II preamp going into a Mcintosh Mc462 amp. One source is a turntable going into a Parasound JC3+ phono pre. When the ARC broke, I tried a Bottlehead Crack headphone amp as a preamp. I was very surprised to see how beautifully this worked. Really rich sound. Maybe it was less accurate (could not do a direct comparison with the LS25), but it was certainly great to listen to, for my taste. I looked into this some and wondered if the lush sound came from the fact that the Bottlehead was using a simple SET OTL circuit, compared to the hybrid circuit in the LS 25. Still you would think that the ARC unit, costing so much more, would sound better.  I am wondering if people have an explanation for this but, more importantly, have been looking into getting a very simple tube pre to use for the phono part of the system. Mapletree audio sells a simple preamp that I believe is a SET OTL (are all preamps OTL?). Al  Freundorfer, the designer and owner, kindly agreed to make me a modified version to test. Some circuits, including a buffer he sells, have the ability to adjust the 'warmth' and extent of tube sound - he would build this into his amp for me (it is available on some of his other products). Is this a good idea? Could I reproduce the effect I heard with the Bottlehead? Not sure how those 'warmth adjusters' work. Thanks a lot for your help.