My guess is that you will need nothing more than the A4, OT, and Brute.
though “need” and what you end up with (or want) are usually different things 
I have a Pulse 2 and love it, and yes it can be sequenced by the OT. Just remember to set the MIDI channel, because if you leave it on the default omni mode, pressing stop on the OT will randomly change the patch back to P001 o.O
Its filter isn’t super characterful but it is versatile. It’s sort of like the love child between a MS-20 and Roland maybe, with moog as a near ancestor. You can do thick/deep basses with it, that’s for certain, plus you get all the crazy modulations and such that’ll let it do some very digital sounding bleeps and wonks. It’s just a really great and versatile synth, and Armen’s in NYC (since you mentioned B&H) sells them for $680 new. I got mine from them via eBay.
i just got the last one at b and h and i played with it for an hour, thing is blast, instantly got me sampling my a4 into it and mangling things up. thanks for the suggestion i havent gotten far into it but i can tell its an awsome addition to my setup.