tube vs ss for pre-amp.

am considering changing pre-amps. system now is gfp-750,marsh a400s,marantz sa-1,aerial 10t.low to moderate volume. adcom pre. is used in passive only.am considering roque or audio research tubed. not sure adcom isn't about as good as i can do in this sys.,but am curious about tubed sound.no dealers in my area for auditions(esp.tube).is there any degree of predictability on what i might hear with this change? also curious about black gate mods for the adcom,but have been unable to contact modifier for info.is this mod only effective in active circuit?any help is appreciated.