As people have suggested, a power conditioner is a good idea... i use a ETA PD8L, and it works great- also means that you can switch everything on in one go, which is nice :) Before you commit to buying a rack case, have a think about what kind of things you're likely to buy so you can buy a case large enough- i'd estimate between 6 and 10u, depending on how many things you're going to put in there.
You can use your GT6 straight into a poweramp, so you could have a setup that is just: power conditioner, GT6, poweramp, which (considering the GT6 is on the floor) means the rack could be as small as 3u, which is nice and portable for gigs and rehearsals :)