I just went through moving my 48x96x30" tank. See the thread in my signature for details. I would tend to lean towards starting to build the tank now and just moving it into the house when you're ready, rather than trying to get it into your office then back out. I have several reasons:
1) it WILL take you longer than you think to build it the way you want it. This is a universal constant and is defied only by very few DIYers. Plus if you rush it, you may cut corners.
2) It is a HUGE pain in the ass to move a tank that size. I just did it, and mine wasn't even set up with fish in the old location. Removing all the sand, decor, and so on, cleaning the tank out, organizing 5 or more people just to get it off the stand into a trailer, then again at the new location to get it out of the trailer and onto the stand - a staging area to put everything while you mess around setting the stand up and working out details - it's a big deal, and I moved my tank from a garage into another garage - you're talking about getting it thru doorways and so on.
3) Never assume that just because a tank weighs around 400lbs and an average guy can carry 100lbs fairly easily that 4 guys can then manouvre a huge cuboid object that weighs 400lbs. Also more hands don't always make it easier. Just picture trying to get a large 150lb couch through a door with 2 guys, then multiply by 3 times the weight and size.
4) the likelihood of damage in transit is huge. I was extremely careful, and I still managed some dings and scratches. Luckily enough it still held water when I got it to the new location.
5) Like someone else said, moving the fish twice in a few months is less than ideal. I know whenever I move my Aro to a larger growout tank he refuses food for at least a month afterward, and I actually lost a 2 foot catfish because I moved him. Better to do it once.
6) To conclude my novel - the construction method I used was unusually lightweight for MFK style tanks, and my tank weighs about 500lbs. I put utility handles on it at every corner and made sure every move was short and well defined - it was still stressful and difficult to move. If you subscribe to the overkill construction method, or if you have to go through a doorway, around a corner, up a step, turn the tank, whatever, it will be even more difficult. Anything is possible, but I wouldn't recommend doing it more than once.