First... I have a Epiphone SG Special and I'm wondering if Heavy Gauge String would fit in the nut. .56? Or I'll be force to bring it to the shop for a nut file...

Second... I will probably go for .12 to .56 or even maybe .13 'cause I tune down to BEADF#B and I don't want to get sloppy and want to sound a bit heavier. So the question is... which brand I would have to look for. I don't have the budget to try 4 different brand and gauge so I have to listen to some of you before buying.

Thank for reading and helping out!
elixirs are good when u can get hold of em, i never can tho so have to go with ernie balls, theyr alrite but rust a lot quicker than elixirs

EDIT: dunno about the first question sorry, floyd rose man ^.^
Jackson DK2 Trans Black

Peavey 6505
Marshall 1960AV
i reckon you shud go with 13.s cuz i have d'addarios 12. gauge on my ibanez iceman and going down to standard B makes them really floppy, maybe even higher than 13.s would be better, but dont expect to be able to tune your guitar back up to standard e cuz it will be a bitch to play with. d'addarios are cheap and pretty good, i can get them for a fiver and they last longer than the ernie ball slinkys ive used
I put roto sounds on my ibanez, they're only 9s/10s but I absoloutely love rotosounds. They do 13s, they're called roto greys and are £3.90, If I played heavy stuff that's what I'd use.
What I want in my rig (Bold = gear I have):
Ibanez SZ-520QM
Vintage VECJ100BK
Epiphone Dot
Laney VC15
Boss GE7
Boss SD1
Zoom G2
I'm gonna put my old Epiphone SG Special's strings, which I don't even know the gauge) on my ****ty First Act guitar that have a decent clean sound. So I'll won't have to tuning my SG on standard anymore. So maybe I'll go for D'Addario .13s... but but over .13s it would be exagerated ?

I'm not used to heavier strings but I suppose that you get used to after a couple of time?