Yes, stock preamp. However, I moved the pickups from my SR705 into my recently purchased SR1305 Premium - also with the stock preamp.
The pickups are incredible sounding and confirms for me that there is absolutely nothing wrong with the stock preamp for my needs. Especially with the 3-way selection of mids on the SR1305 verses the 2-way mid freqs on the SR705. The stock EQ points on the SR1305 work exceptionally well with the DCB pickups and I will not be changing it out.
As far as A vs. B pots, not quite sure. This comes down to mostly personal preference in regards to how they work (linear vs non-linear).
Here is a nice
thread explaining other people's take on the debate. I would think 500k for the pots would be in order for the humbuckers, but I would definitely ask Aguilar what they recommend, especially for your preferred passive/active, push/pull wiring.
Here's a TB
thread discussing something very similar to what you are looking to do. Hope any of this helps - best of luck with everything!