heya, the Aquaone packages are really popular here, i have two AR-380s and have never had a problem with getting parts. I chucked out the carbon pad and replaced it with plain filter wool, and this is the main part that you replace regularly, so it saves a bit of cash.
Having said that, i probably wouldn't go with aquaone for a bigger tank (the 380s are around 34L), my bigger tanks are custom as i want the better filtration/lighting that you can have when you assemble your own setup. (my 380's are fry tanks).
Also, shop around, as the tank/ cabinet all-in-one setups can vary quite a lot in price for the exact same product ( ie the 380 was selling for $170 in one lfs, and on special for $99 in another...)
HTH, merry.