Help me decide on a new tank size

[Ross]

Well I'm going with the 36wide, 18 deep, 24 tall. Aproximatly 67 gallons
I'm going this way for a few reasons
More likely then not, when I decide to upgrade later, I can reuse this tank for a few of my discus (they prefer taller tanks)
Visually it will fill the space better than a 18" tank.

Now for the next task, where would you put an internal overflow?
I havent tried to aquascape with internal overflows, but for the stand and location, I'm thinking that the rear left will be where I go.
I dont rally like the idea of an external overflow since the back of the tank would then have to be away from the wall further, and its in a high visability spot.

Thoughts opinions, do's and don'ts, etc?