I have a pair of Genelec 8020Bs that I bought for mixing and they sound absolutely great on jazz combos, rock bands, chamber groups, etc. Particularly the phantom center image-- really out of this world. But I could hear them struggling with the bass on Beethoven's 7th. It's got me thinking about a sub for them. Genelec recommends the 7050B. Does anyone have experience with different subs in this context?