I have an Ibanez RG490F (Floyd Rose-style bridge) and my tuning is: A-E-A-D-F#-B. I use D'Addario 'Jazz' Strings (13s) (I play hardcore/metal, not Jazz!), and the tension is *almost* identical to the 9s the guitar had been set up with before I tuned down. I only had to adjust the tension a little - the set up is not 100% there yet, but it's really very, very close!
I've also done this to a Marlin (no idea what type, horrible horrible guitar, but used as the experiment!). That also worked fine, but if you do switch to 13 gauge, or even 12 gauge, string sets, make sure the bit where the string goes to the machine heads at the end of the neck is big enough to cope (or metal). Cheap guitars often have a plastic bit for the strings to sit in, here, and they can snap if you don't file them down - this would be a nightmare!
(I'm talking about the "other" end from the bridge, but I can't think of the word just now!).
I use Stubby Triangle picks (2.0mm). Work nicely :)
Roo