On string gauges
I spent quite a bit of time experimenting with string gauges. D'Addario used to have a tension chart available on their site as a PDF file. It's quite useful, but I can't locate it on their "improved" site.
Tension is just one part the equation. Another factor is that the amount of metal moving in the magnetic field of the pickup affects the relative loudness of the string. These are the two most noticeable effects of a string's gauge.
A secondary effect is the stiffness of the string. Stiffness, for a given kind of wire, is related to the diameter. (For wound strings, the diameter of the core.) Stiffer strings don't intonate as well. For this reason, an unwound G string often sounds "off" compared to its neighbors.
I got into trying different string gauges to solve two problems. I found the B and E to be too slinky. Also, I found that the lower strings had too much emphasis - my guitars, given my technique, sounded bass-heavy. Putting heavier strings on the top and lighter strings on the bottom solved both problems. I ended up with a set that's kind of like a set of 10s (with a wound G) on top and a set of 9s on the bottom.
I use D'Addarios sized 9.5, 13, 18W, 24, 32, 44. (The 9.5 and 44 are actually the half-size in between the usual size of D'Addario's 9 and 10 sets.)
If you wanted to get the same effect in a heavier gauge, you could pick the gauge of your high E, note its tension, then scan the tension chart and pick the remaining strings to have about the same tension when at pitch. That's how I arrived at the set I use.
Finally, note that you can't apply D'Addario's tension chart to other brands. It'll almost certainly be wrong for the wound strings due to differences in core size. It might also be off for the plain strings if there's a difference in the composition of the metal.