You have a speaker and several amplifiers that share a fairly "cold" characteristic, especially in the treble range. Frankly, you'd be more likely to attain the sound you seek by changing either power amps or speakers, depending on which you are more committed to. However, if it is the preamp route you want to take, keep in mind that there is the variable of the preamp itself, and then also the variable of what tubes you put in it, if in fact you go with tube topology.
At various prices, some options: Quad QC-24; The Sunfire Classic Vacuum Tube Preamp -- fnd some NOS Telefunken tubes for it; Audio Research SP16 or SP16L depending on whether you need a phono stage; McIntosh C2200 will definitely solve your problem; Melody SHW1688 -- like butter, and perhaps the best preamp I've heard to date. In solid state, it would be worth considering a McIntosh C46. It's revealing but not bright, and the 8-band eq does allow a touch of judicious trimming.
Phil
At various prices, some options: Quad QC-24; The Sunfire Classic Vacuum Tube Preamp -- fnd some NOS Telefunken tubes for it; Audio Research SP16 or SP16L depending on whether you need a phono stage; McIntosh C2200 will definitely solve your problem; Melody SHW1688 -- like butter, and perhaps the best preamp I've heard to date. In solid state, it would be worth considering a McIntosh C46. It's revealing but not bright, and the 8-band eq does allow a touch of judicious trimming.
Phil