Leaving aside the fact that the Fostex FE168Esigma back-horn is something of a mismatch with the hemp drivers mentioned, according to their specs. at least (to each their own & all that), it really depends how much you want to spend, and the nature of the crossover you're planning on.
What I can say is that I like the T900a; it's an excellent performer, but comes a rather hefty price. The T90a is also quite good -not as good as the T900a, but being a cheaper model, you wouldn't expect it to be. At slightly less rarefied levels, you might want to look at the gold-dome Audax, or some of the pro-audio units available.
