Uh is it just me or did anyone notice the word rap in the question.

Ok arrangers are cool and all but they are not used commonly in hip hop production. Sort of the wrong tool for the job if you structure your rap the musique conrete manner (found sounds sampled - mostly found in the composers record collection). Not to say that it is not possible but more hip hop or rap I hear from arrangers sound like it is from an arranger and is normally pretty weak as far as that style of music is concerned. But this is a personal pref.

Might it be better to make some of the mention of gear that is proven to be pillars in hip hop production like an MPC series, ASR, EPS, SP1200, and just about any other sampler.

They are just some of the equipment you find people who make this music use. (not to say jump on the band wagon, I personally prefer my kurzweils myself)

It seems the computer is the best in road to this type of compsition style these days, and much can be done with fruity loops and Taureg as examples at the fraction of the cost if you own a PC and often with better results.

just a thought