My recommendation will be different then most. Do some math first. Find out what the output impedance (Zout) of your source(s) are and the nominal voltage(s) (Vrms). Then determine what the input sensitivity and input impedance (Zin) of your amp is. Together this will determine if you need any gain in your system. Actually you should also determine if the full output of your amp is sufficient and neccessary for you speakers, but assuming this is so, that will suffice.
I say this because most preamps have quite a lot of gain. More gain means more noise and more distortion most of the time. This may be nice for the system that has too much odd or higher harmonic distortion but isn't nice in general. Some tube preamps are different then most and have different gain structures, so knowing how much you need can help us guide what tube preamps might be best for you [if you have determined that tube preamp is definitely in your future].
This might seem a bit too objectionist to you, but mind you I like tube equiptment and value the right profile of distortion. I just think that too often all the rest is overlooked even though it should help immensely.
