One of the main reason why I am kind of saying away from a bigger system in the house is that I don't want to potentially make a mess in the house and ruin my wife's precious floor lol. But yes I definitely know what you mean. However I do spend alot of time in the garage.The buy on the tank is nice, but be careful about a big tank in the garage. I have a not-so-big 4' 90-gal in my basement garage, and even though I spend a lot of time down there, it really doesn't get the attention it deserves.
Proximity to your inside main DT is important. Think about water changes, ambient temperature changes, evaporation and the humidity generated in your garage etc. Things can be very different in a garage. Do you spray paint projects there, create wood dust? There's a lot to think about.
I have found my garage tank is best used as a "utility tank" where I experiment with new equipment, try new aquascapes and best of all, don't care if I make a mess on the floor. But man!!!, that's a big tank to maintain in a garage.