It's as much about cost as it is about price.
My practice amp is a Phil Jones Double Four, which is smaller than most of the super cheap 8" combos, yet sounds great - even with a low B.
My favorite small cabinet would be the barefaced one10. It sounds absolutely huge at bedroom volume levels - and you can pair it with any head you like.
Some people will claim that any bigger amp works because they all come with a volume knob - but when I sold my barefaced one10 and bought a Super Compact, I found that the Super Compact is too loud for quiet home playing - it surely does go down to bedroom levels, but there is a point where it "wakes up" and sounds rich and full, and at that point, the chinaware in the cupboard opposite already rattles. The one10 sounded much better at lowest volume levels.
If you're looking for budget solutions, I'd say the not-the-lowest-price-tier 1x10" combos work for four string; for a five, a 12" might be the better choice.