If you've got a passive now then it's generally going to be hard to find ANY preamp, tubed or SS, that can match the transparency you are now hearing. Having said that, passives may lack the extra balls an active linestage will give you, and probably lack that extra bloom that tubes bring to the table.
Try to find the most transparent tube pre you can afford. Mine is a little long in the tooth now, but if you can find an Audioprism Mantissa (or it twin sold under the Red Rose name) you might be very happy.
Try to find the most transparent tube pre you can afford. Mine is a little long in the tooth now, but if you can find an Audioprism Mantissa (or it twin sold under the Red Rose name) you might be very happy.