in my experience you get the best results from putting together a set of singles.
i started out on .115 / .85 / .65 / .45 - this was OK, nicely balanced but still a bit low tension for my liking.
settled on .120 / .90 / .70 / .50 - perfect! nice and tight, not too much so. the low C was punchy and bright and tension was even all over. these are Rotosound stainless, by the way.
if you use the sets mentioned above - nae offence lads

- you risk uneven tension across the neck.
whatever you choose, make sure you adjust the truss rod and intonation. i found i had to file the nut a bit for the .120 guage low C.
there's loads of more knowledgeable folk on here, though - do a search for down tuning or drop tuning
