Strictly Ernie Ball
I only play Ernie Ball. No other string offers me what I want.
For a 7 string set I enjoy the Cobalt series.
They kept that brand new string sound for about a month on a guitar out of the case being played everyday.
They still sound great though, like a set of traditional Ernie Balls after about a week of use.
They definitely improve the over all output.
I suggest these before buying new pickups if they're not quite hot enough. They might change your mind!