I infused my Ace of Spades, Fabian Strategy, and Tlaloc to 320. I figured these weapons were special enough (being class specific quest weapons) to get up to the max attack value. My inventory was filling up with 320 weapons from completing Oryx challenges, so I had to get rid of some. My next step is to have my Immobius and Susanoo at 320 attack. I already have a 320 Stillpiercer. Now if the Warpriest challenges would award me 320 sniper rifles and not heavy weapons, that'd be great.