Reflectors are absolutely necessary if you want to light a specific area. Without them, you'll probably be wasting at least 75% of the light (top and sides of bulbs). And reflectors are not cheap (about $20 each when I looked). By the time you add reflectors (if they even fit in that fixture) and bulbs, you'll have spent at least as much as a fixture that includes them.

Good find. This is the first T5HO in a Home Depot store I have heard about. The price is good -- I bought my Lithonia Z-strip 2 lamp 4' T5HO strip light online for $50. Do you know if the one you saw can be detached and used as two separate units?

To be more precise, can these be used side by side instead of in line? I understand that there is a single ballast so I wasn't sure.

I am not sure. I am guessing probably not unless you can fold it at the center.