Hi Xenon,
I think that tray is overpriced. I'm sure if you went to your local hydropinics store they'd have something equivalent for half the price.
The lights are ok but they aren't grow lights. Small niggle, but I'm sure they'll do ok. Things will grow under them and who knows they might give identical results. I've only tried fluorescents and led's but there is a difference between my discontinued Ikea growlight they used to sell and equivalent bulbs I've bought since. The Ikea bulbs make stuff grow but I am thinking by now the results are not as good as other bulbs.
The lights you have should be used if height is a limitation but it sounds like you can ultimately control the height in which case this light would light up the area too:
Amazon.com
I've tried this light, it works great. The difference is hard to describe but my attempt would be the garage lights are like portable radio's, the more you place next to each other the louder they get but take the plant grow light it would be the equivalent to on outdoor sound system the whole neighbourhood could hear. You'd need a lot of radio's and even then I don't think you could generate the bass, ok off topic but the grow light you cannot look directly in to - it is as bright as the sun, the garage lights are designed to gently illuminate a garage. The more you use the brighter they will be but you will still be able to look into each one without discomfort.
That's the difference and the results should be accordingly.
Like I mentioned weaker garage lights are great when height is a limitation as they can be used as undershelf lighting where higher powered grow lights would just be too strong but I'd go with the grow light, it has more wavelength and more power to provide energy (think one big sound system is better than 10 portable tinny sounding radio's)