I would most likely personally keep the strength at 80 like it is, raise the attack and def to anywhere between 90 and 99. When boxing with these stats, you will be able to decide what way you want to go with your levels (if you want to change them at all).
Raise your Magic and Range to a decent level (if you CBF with range, atleast do mage), do Lunar Diplomacy so you have Lunar spells (and you can do the quest/subquest without prayer, happily). While Lunar won't help you with staking, it is an extra positive for your account.
Another plus to getting your magic is that if you ever decide to get Ancients for mage boxing, you will be able to actually use it lol.
Getting range up will mean you can also do range stakes if you decide to (and you don't need prayer for that, which would be a positive for a boxer).
I wouldn't recommend doing any PKing unless you wanted to go much higher with your prayer, but then you would basically be a main.