What size of the tank do you wish to have?

PetSmart got just the thing for your dream plan.

Here is the product link,
90-gallon acrylic tank with dimensions of 48" L x 18" W x 24" H
You can save 15% on it with free shipping if you buy it before 1/19/2013. I just made a thread with the coupon code here.

You know we both have almost identical setups right now, but my future plan is way above yours. The height and the width can stay the same as in your plan, but the length should be doubled to 48" x 2 = 96". It will be exactly 180 US gallon. I will be able to get larger fish like Discus.

It will have two canister filters, one on each side. I have my eyes on EHEIM 2078. Two of them will give me total flow rate of 980 gallons per hour, which will go through all of the water 5~6 times each hour depend on how much water I actually fill the tank up to. You can never have too much filtration.

It will of course be a planted aquarium with about 3" thick of eco-complete as substrate.