Bareknuckle! Some people swear by pairing medium-output BKPs with the Diezel amps, like below 10kOhm was one those suggested limits flying around... it hammers the preamp less and gives you a bit more "bloom", lets you hear a bit more of the gain structure; the Diezel amps give you all the clarity and gain and punch you could ever want so you don't necessarily have to go ultra-high-output to get more, the amp is doing it all for you, so you can "relax" a little on the pickup-output side.
Of course that also depends on what you are playing and if you want or need the tons of focus you get from a high-output pup! Alnico Nailbombs are definitely one of those great modern allrounders, probably one of BKP's most popular pups; Aftermaths especially for extended-range-guitars, Painkillers for a very aggressive, cutting tone, Warpigs for more deep "brutality". Or so is my own take on some of their most popular pickups.
You can also email BKP directly, give them an idea about your gear and the tone/feel you want, what's important for you and they usually reply very quickly with suggestions!
