You don't need a sump...... But it can drastically improve the quality of the tank. Most of the all in one nanos do not have provisions for an over flow. Please keep that in mind. You might just want to get a 20g for $20, an overflow box for $40, a nice high wattage T5 light (or even better yet 150-250w metal halide), a 10g tank for sump, a nice Eheim hobby pump to lift the water back up, a small ASM skimmer to clean the water. My guess is you could get it all for $300 or a little less depending upon how much you research. Oh and I forget you Canuks have to add about another 20% for exchange rates. Canadian quarters, hah what a joke.
The most important step you can make is to nail down exactly what you want from the tank right here and now. You can always "grow" into the tank but it will cost a lot more then just setting it up the first time.
So are you interested in SPS, clams and inverts?
Are you interested in brightly colored puffy corals like brain corals or hammer corals?
Do you prefer mushrooms and zoas?
Do you only want a fish tank?
Do you want a mix of everything, if so then figure you'll need the whole package. A softie tank, shrooms and leathers only, will need minimal attention. LPS tanks will need better lighting and flow. SPS and clam tanks will need the cleanest of water, highest of lighting and flow. If you plan to mix then plan on an SPS tank so you can grow into the tank instead of growing the tank into your needs.