Hipshot A's in Aluminum (I prefer the "snap" of it to the tonal qualities of the Brass models) as you have the option of choosing between several different string-spacings, and one is *exactly* what I find to be perfect for my personal playing. I could also do the same with a Kahler, but I've heard it's much more of a PITA to do so.
If I ever get a custom bass made I might consider Hipshot"s "Triple Lock Down" single-string Mono-Rail pieces as I general like the idea of keeping each string physically separated from each other to reduce crosstalk to a minimal amount, but the A's are so very workable and perfect in terms of spacing (something I took years to find exactly what worked best for me) for me that the positives very well might not be worth the change.
If I ever get a custom bass made I might consider Hipshot"s "Triple Lock Down" single-string Mono-Rail pieces as I general like the idea of keeping each string physically separated from each other to reduce crosstalk to a minimal amount, but the A's are so very workable and perfect in terms of spacing (something I took years to find exactly what worked best for me) for me that the positives very well might not be worth the change.