Well, any drain that's drilled through the tank wall is a better option than a HOB overflow. There might be people that post on the thread that tell you "I've used X HOB overflow for 5 years now, and no problems". That may well be true and honest, but there are also lots of folks that have emptied the entire sump's worth of saltwater over the top of their tank and onto the floor/carpet with an HOB overflow.
Since you're willing to drill the tank, a 40g breeder with one of e-shopps 600 or 800 gallon "herbie" overflows would be quite nice. Perhaps not as snazzy as a rimless starfire tank, but a whole lot cheaper, and if I were forced to decide whether to have the tank look cool or buy more interesting fish or coral, I'm going to choose the DIY route and the fish/coral every time.
There is, however, one consideration you should make. It's likely that you're going to decide you want 3 primes over a 3 foot tank in the future to avoid shadowing, so that adds to the cost of going with the 40g breeder, or other 3 foot tank. But if you build a stand, use a tank for the sump, and go with a self-drilled 40g breeder, you'll save way over the $$ required for a couple of extra light fixtures. Yet another option is keeping your nano running with its current prime fixture, and go T5HO over the 40g breeder. A 6-bulb T5HO ATI SunPower would give you all the light you'd ever need for anything you care to keep, even SPS, and it will fully illuminate the tank with no shadowing whatsoever.
Edit: If you want to see a video of IM's EXT40 like I just got, Jake Adams from Reefbuilders set one up in his studio and just did a video on it. Cool tank, but I wouldn't personally put a yellow tang in a 2' x 2' tank, nor would I go bare bottom. But it'll give you an idea of the aquascaping room you'd have in a 2'x2' (that will be far easier to illuminate with 2 AI Primes, if you decide to go that route).
