Yep, room for growth is the key.
If you buy the bare minumum now, then 6 months or 5 years down the road when you decide to upgrade, that will just be that much more equipment you have to buy to do it.
As long as you're sure that brewing is a hobby that you're going to stick with for a good, long time, then you can never go wrong by going big.
You can always turn down a gas regulator, or close a ball valve a little bit, in order to make overkill gear work with your current system. But if you have little gear and are trying to move to a big system, you can't turn things up the same way you can turn things down. At that point you're buying new stuff and hoping and praying that someone on craigslist will give you a fair price for the expensive stuff that is now useless for you.
Just buy the big stuff right away. You know you're going to go bigger eventually, so why not just get that component taken care of right now?
It may or may not take you a little longer to upgrade your system with that approach, but at least when you buy big you don't have to worry about replacing anything....