There are Tube Pre Amps that are going to influence the End Sound.
It is important to know whether a design is to influence the produced sonic with a quite discernible rich tone, rich tone, or transparent for a Valve.
No point spending monies on a device that influences in a way that can quickly become a detractor when the sonic of the device becomes quite noticeable.
EAR produce Tube Pre's that are a injection of a Rich Tone, one model has been demo'd in a system that is familiar to myself and was very much liked.
A friend who owns the EAR Acute and others who own their Power Amp's have proven the EAR designs responds very well to tube rolling.
Tube rolling is a area worthwhile budgeting for when shaping the upstream sonic for the system.

