They're fixed bias EL84's, so no need to re-bias the amp. Your TSL on the otherhand uses EL34's which will need re-biasing.

JJ tubes are great. I tell Bob at eurotubes how things sound, and then how I want them to sound, and he delivers! My classic 50 2x12 combo has an awsome chunky metal rythm sound now. Before it was more like Skynyrd or 38 Special type overdrive (which it can still do very very well), but now the clean channel breaks up a bit earlier than before which gives it a really fat/thick tone, and the dirty channel can go from dirty blues to metal chugga chug(especially through my marshall 1960A 4x12 cab).

New tubes can really liven up an amp, and if you want can drastically change your sound.