Surprised nobody mentioned Audible Illusion given it's sales and mpoularity as a loid glass pre.Depoends a lot on how much "bloom" you want.Some tube pre's dont' sound very "tubey" any m,ore.More and more solid state has attributes of tube gear )warmth,holography,more natural midrange) but tube gear (especially pre's) have more extended frequency extremes and tigher,punchier bass.I would say that in poast with a tarde off for noise that Conrad Johnson would give most "tube sound" (maybe certain AR models) but now CJ is less noisy and has better overall sound (bass not as "loose").You need to read about various pre's.But I think TVAD is right you will get different sound but if you expect "Nirvana" in a box you might not get it.Yet still might be good move.Alternately the better op amps in some digital players means that forgoing pre might be your ticket.Many audiophiles want sound of source and amp and nothing from pre,a pre that has no signature,Some go with passives but because they have constricte dynamics in general I am not one of them.So many models out there do your research and try to listen when and where you can.If you go to ww.6moons.com the not cheap Supratek will be their editors choice (I liek thier Blue Moon awards).Stereophiles buying guide gives so many choices it just shows what's out there not narrowing down choices.Also ask at Audio Advisor.Features,the difference in what tubes are used (poular EL34's which I use excell in mids.KT88's have more dynamic kick and bass control etc).Like I said some want not to hear it at all but to me I's say listenm to CJ,AR,neutral BAT,bang for buck Rogue or Modwright,Audible Illusions etc could take thoguht and time to listen.But because many feel it's signature not just function is the "heart of the system" when matched soudn wise with your gear and your ears the quest can be fun and really pay off.
Chazz
Chazz