Perm upgrades a terrible idea in my opinion because once you get to a certain point... you just no longer need money or experience... You need to loose some when you die... So if you kill more than you die you will get points to be able to afford your systems. Fortunately there are no negative scores, so it is fine to die if you got 0 points. That way if you get up there you need to stay up there, and upgrades are not permanent, just to make sure players that player for a longer time are somewhat even to the players just starting off/don't play as much.