Which tubes are most successful with Pipedreams?

I currently have Levinson Reference Level front end equipment with the exception of the preamp which is the 38S and amps which are 20.6's.

I recently purchased Pipedream Hemi 18's which I am going to keep.

I would like to get a richer, warmer sound of reality. I very briefly heard some SET's which helped a great deal. Should I consider first a tube preamp or amp? Which ones? What cables might move me further in that direction? Other suggestions?

Any help will be very much appreciated.
I own the 21 s . I have the gamut 200 mk 11 and the sound was dynamic and full of life. I also have the Classe Omega power amp and it alternated between towers and subs but its ultimate control and power reserve made the sub match ideal. I thought I was set until a friend brought a pair of the just released Cary 211 signature special edition mono bloc amps over.{They just won one of the products of the year at Positive Feedback btw. } The difference right out of the box was astounding. Clearly besting both the Classe and the Gamut in nearly every conceivable area except for EXTREME pasages and I do mean extreme where the Classe never ran out of steam. At any other level , the Cary was the clear winner. You want a richness that is best described as liquid lightning ? You want a depth in your Pipes that draws you into the music? I put them on my ESP Concert Grands and I was stunned at the combination as well . I think the Cary 211 s are a must on a short list .
Give HOLM Audio a call. They are located in the Chicago area. He sells the Pipedreams and usues a varirty of tube gear for the towers and ss for the subs. Frankly they always sound very nice when stopping for a quick listen.