Trooper 1,
As the GML of the Singapore Garrison and a Sandtrooper/Bounty Hunter, my personal opinion and advice to you is to get yourself a Kit and have it fitted to yourself. Gettin ready made armor, especially if you're going for a movie look, just isn't gonna cut it.
Most, if not all of the troopers I know, got themselves Kits, read up on the DIY bit and put together their own armor. As for those that needed help, there are builders that will help, but will still require the ones they're building for to be around for a proper fitting. In short, if you want a proper fitted armor, either do it yourself or have someone with the experience do it for you [with you being around for the fitting.]
Last but not least, FX armor is affordable but nowhere as accurate in both size and 'cut' of the Stormtroopers you see on screen. best way to describe it, FX Helms are at least 10% bigger than the Movie Helms, armor less so.
Keep in mind that sometimes it's not practical to have ALL the bells and whistles intergrated into your armor. Alot of things can go wrong, and add to that, the weight issue of all the addons with the power supply [batteries] etc.
Remember, comfort is just as important as free movement, you'll need to be able to move like a trooper and not a robot. And you don't want to have armor bits cutting into you, especially if it's poorly fitted.
Don't rush this, do your research, and hit your fellow 501st members in your area and ask em questions...I'm sure they'd be more than wiling to help you out with your armor queries. Get the relevant info you need, decide carefully and then make your buy.
And you don't always have to buy everything at one go...and like everything else armorwise, upgrades will always be the norm.
Good luck and stay safe,
Tim.