Of the lighter ones I have owned the heads I currently enjoy are
Orange Terror Bass 500. It doesn't have a great variety of tones in the bin but I really like what it does - not everyone does so caveat emptor. Insanely loud, old school rock amp.
Second place goes to Quilter Bassblock 800. Around the size of a box of matches, 800W, easy intuitive controls that make it impossible not to dial in a good sound, with an interesting break up once the gain gets increased a touch.
I'd put those two above the Mark Bass, Genz Benz, TC Electronic, Eden, Ashdown, Harley Benton (= Promethean, Red Sub) heads I have had.