So far you have been given good advice. If you picture the sound in your room like a pot of soup, you will understand it better. Anything you put in the soup will alter the taste a bit. Although separate, if you view amp and pre as one you'll get a better picture of what they contribute to the overall sound in your room. A good amp would be a waste of money. A good tube "integrated" would improve the sound. "Primaluna" integrated is the most "bang for the buck", and that's what I recommend.
In regard to "tube" or "SS", the only way you can find out; is to try tubes.
In regard to "tube" or "SS", the only way you can find out; is to try tubes.