This topic comes up from time to time, so checking the archives may turn up opinions that will not come up in this discussion. Most go with tube preamps. I went the other route and went with a tube power amp. However you introduce tubes, once you do so, you will notice how the 'texture' of the sound changes. The sound will seem just a tad softer, just a tad less focused, which tube folks find very pleasing. The edges are not as sharp. It is not terribly unlike hearing a good recording on both vinyl and CD ... both have their merits, but they do sound a tad bit different.
If your speakers require a lot of power or you listen at loud levels, you may have to go with a solid state amp. Tube power isn't cheap. I already had a Musical Fidelity CD/ Preamp that I was very happy with. The MF 300 power amp was just a tad too present in its sound, so by adding the Prima Luna PL5 the sound softened just a bit which was much preferable to my ears.
Sorry to focus my comments on the 'tube' sound, but it is important to know what to expect. You could also go with a tube integrated amp ... Prima Luna makes some great ones.
Rich