To be honest, I was avoiding watching subbed stuff for a long time as well, but then I finally decided to go for it with High School of the Dead, and it opened up so many doors. And filled up my hard drive. :'(
If you hadn't said no subbed, I'd totally say TANTEI OPERA MILKY HOLMES. It has "tantei" and "Holmes" in the title. Clearly, it shall be a fantastic detective series. But it's also about little girls, so maybe not.
There are a lot of series where the English dub is better than the Japanese.
And dubs have been getting progressively better since the 90s. Aside from porn, almost everything dubbed in the past 5 years has been really high quality.