You can have a lot of fun playing with some tubes. Most commonly for people to dip their toes is a tube preamp and solid-state amp. As for speaker demands with tube amps, try not to combine low power single ended amps with low sensitivity or hard to drive speakers. That goes the same with any amp/speaker combos though. A great cost effective step into tubes, look at Tubes4HiFi. Kits available if you're handy with a soldering iron or assembled for a couple extra bucks. Hell of a good way to get your feet wet.
