There is no best or perfect speaker. It is all a compromise. Different speakers have certain strengths and weaknesses. Also speakers can be system dependent. There needs to be a synergy. You don't say what the rest of your system is so it is hard to make suggestions. The Dead loved McIntosh tube equipment. They were even a McIntosh dealer at one point.
I would listen to every speaker you can to get a feel for which ones you like. Try to listen with equipment similar to what you have. Use the same music, music you are very familiar with. Make a list and then whittle it down. I am also a dead fan. I want the illusion that the band is right there in the room. The tone of the instruments and voices needs to sound natural and not artificial. Most dead is very well recorded. Even the soundboard recordings of concerts sound really good.