FP-4 is definitely finer grained than HP-5, but maybe not as much so as you would expect. Delta 400 might be a good idea, and XP-2 is definitely worth a look. (XP-2 has quite a different structure than HP-5. It is a color negative film that gives black and white results. Those results are quite spectacular.) When you go to bigger print sizes, a tripod is the most important thing you can use to increase sharpness and print quality. Unless you shoot at faster than 1/250 second, a tripod is an absolute requirement for big prints, and it often helps even at fast shutter speeds. A cable release and mirror lock-up also help noticeably.