Agree. All the developers you have used are solid classic developers. If you are not happy then you need to figure out what you are doing wrong rather than look for a magic bullet. I would stick to any of the three developers and mix it yourself. Sprint is a particular favorite of mine and is a liquid, and D76 and Xtol are superb classic developers. D76 is a true classic and Xtol is a modern classic. If D76 (or Xtol or Sprint) mixed correctly is not doing the job then you need to double check your technique including metering and exposure, temp, agitation, dilutions etc. BTW both Sprint (a Phenidone/hydroquinone developer) and Xtol will likely give you a higher effective film speed than D76 but you should at some point do your own film speed test using your selected developer and see, it is more important specially since you are not happy with your current result. Is your meter accurate? Is the thermometer accurate? Mix/dissolve the chemistry yourself to take out that concern.