Tubes in an Anthem integrated 2 Sovtekv Mulard

I am playing with an Anthem integtrated 2 and am wondering about what experiences people have had with tubes in the preamp section. My take is the Mulards are alittle laidback and sound somewhat rolled off compared to the stock Sovteks.but i have spent very little time comparing. I do listen to rock and blues. Thoughts?? keith