Huge difference. Going from SS to tube is great if you have very efficient speakers. Otherwise, you will become frustrated quickly. How efficient? My rule of thumb is 90db or higher - but if your tube amp has low power, then much hire db efficient speakers are needed. Room size is also key. If you have a big room (say anything bigger than 10 x 15), then you will need even higher efficient speakers.
The other option is to look at some big tube amps like the Mcintosh 2301's. Then, 90db efficient speakers or higher should be fine IMO.
Mike