I really like the 906 and Fathead combination for micing cabs. I don't find the Fathead 'dark' per se - it does have somewhat of a classic ribbon sound which smooths and attenuates some high end, but if you don't want that I'd suggest not using a ribbon (though some of the newer designs like the Royer do seem to have more high end response - but yeah they are not cheap!). Also depends on the tone - for retro/vintage sounds I've used just the Fathead by itself, and for more modern/cutting tones I'd reach for the 906 or possibly a 57 (though most of the time I prefer the 906) and the mic pre - I often pair the Fathead with a brighter/tighter pre (like an API) and sometimes pair the 906 with a smoother and arguably darker pre like a 1073. And of course placement factors into the picture too - if combining a ribbon and a non-ribbon dynamic, can position the ribbon pointing closer to the dust cap and the other closer to the edge so the net result may be about equal brightness.