upgrade from Audio Research SP6C

Hi, I have a SP6C with VT100. I like the 3D sound of SP6C. I compared it side by side with CAT SL1, Krell KRC-HR, SP9, LS7 and SP16. The CAT is very neutral. KRC-HR is more focused and has better image. LS7 is so sweet in mid but lack of bass. SP9 and SP16 are also on neutral side. None of them has lush 3D sound as SP6. My favorite media is female vocal. I also have 30% rock and classic music in my library.I heard a lot of positive for Conrad Johnson. That brings me a question: should I try CJ preamp? Which CJ model should be a upgrade from SP6? Or should I go up with SP8 or SP10? I don't know if there is a big difference between SP6 and SP8/SP10?