In these 'what to buy' cases, there is usually a suggestion by someone that the op go into a shop, road-test some cabs / amps / basses / leads / leather trousers / whatever, and buy the one that he / she like the sound of.
That would have worked here surely?
I think the op is fixated on achieving a 'flat' sound above all else (or just trollin'). I bet a good proportion of us, me included, don't know or care what 'flat' sounds like anyway.
ftr, I like 10's too, but my cab is a 2x12! And y'know what? I don't care if it's flat, spherical or an accurate representation of that Kardashian bints' mahoosive arse, if it sounds great, it sounds great.