i have a 1.54ctw eternity (22 stones, 2.2mm), and it looks great with my .52ct solitaire because of the wide band. however, i don''t really like it next to my 1ct e-ring, which has a thinner band. i would like something larger to go with my eternity band, something between 7mm and 7.5mm.
the only way to know what works best for you is to try on rings.