If you need 4G you'll need to get the AT&T/T-Mobile version (also might be listed as the "GSM version"). I'm not sure how things stand in terms of SIM-unlocking, so you'd better get a Developer Edition. The Verizon version also works over here, but not in 4G.
Considering how cheap the 16GB versions are going for over here though, I'd seriously think twice whether you REALLY need 32GB! At the time I imported mine it ended up costing me only £40 or so more than a 16GB edition, but considering how much the 16GB version has dropped the difference would now be a lot bigger. If you're gonna have 4G with 3's all-you-can-eat deal I think you can get away with streaming all the media you need and using services like Dropbox for everything else - 16Gb will be more than enough for your apps and games! Even after installing ALL THE THINGS on my 32GB one I still have 19GB left, and that's with me never having bothered to get my videos and photos off it since I bought it!