If I'm looking for "Tube Sound", why would I put a Tube Pre in front of a SS amp?

The reason to put a tube preamp with solid state is if you have to compromise and want the benefit of tubes, a tube preamp will give you smoother sound and more detail than a solid state preamp. There is no way to gloss that problem over downstream; once you've lost that low level detail its gone.

However, if you really want to treat yourself go with tubes all the way. That way you get the additional benefit of reduced higher ordered harmonic distortion, which to the ear sounds like brighter and harsher, and is the thing with which transistor amplifier designers struggle. Its true that those harmonics are minuscule compared to the greater amount of lower ordered harmonics typical of tube amplifiers, but the ear uses the higher ordered harmonics to calculate how loud a sound is and so is far more sensitive to them, in fact more sensitive than test instruments.

FWIW, its not beneficial regardless of a tube or solid state amplifier, to working with a speaker that is 'hard to drive', especially if that hard to drive aspect is low impedance. The simple fact is all amplifiers will make greater distortion if you make them work hard, and the distortion we are talking about is audible as a harsher and brighter top end. You can see this increased distortion in the specs of all amplifiers! IOW if high quality reproduction is your goal you are simply better off avoiding speakers that are hard to drive.

"However, if you really want to treat yourself go with tubes all the way. That way you get the additional benefit of reduced higher ordered harmonic distortion, which to the ear sounds like brighter and harsher, and is the thing with which transistor amplifier designers struggle. "

I would generally agree with the comment above. To me the really big difference AND big deal with tubes vs SS is the harmonic resolution AND that undefinable attribute of "presence" that the BEST tube designs really deliver that I rarely hear consistently with SS. I try to be fair minded, objective and balanced in these discussions but I REALLY agree with Atmasphere's comments. I have a good audio buddy, all tubes over the almost 20 years I've known him that has gone over to the "dark side":), tube preamp, ss amp, i mean superb SS. While I really like the presentation and at times it makes me question things, over time I notice that it just does NOT have the emotional connection to the music as good as it is. To each his own and remember this one simple point, it's all an illusion anyway, whatever floats your boat is most important, just listen and enjoy!

Lots of great comments on this thread. One thing not mentioned is that with tube preamps, most use tubes that are:
- low in number 
- in sizes that plentifully produced by many manufacturers both past & present
- sonically different than other varieties of the same size tube
This leads to the potential sub-hobby of tube rolling. Hearing the differences between e.g. a Mullard vs. Telefunken is fun and interesting in itself, and let's one take the task of finding system synergy to an art form. My old friend and occasional poster, @mechans, shared a tiny portion of his great tube rolling knowledge with me, lending multiple pairs of 6922, 6DJ8 etc. to find out what works best with my gear. For those interested, it's fun and sonically rewarding with good tube preamps especially. Cheers,
Spencer

@sbank you might try out a preamp that uses 6SN7s... once you hear what the 6SN7 does its hard to go back to miniature tubes.

@atmasphere, Ralph, I did own an MP3 for a time. 

My post was intended to bring up the pleasure of tube rolling, nothing more. Cheers,

Spencer