i <3 the t5 lights. So efficient and awesome output. 20,000 lumens is amazing when it comes to growing. I have 6000 lumens or so in my grow box and it is alright. More light is better though! (more than enough light for cloners too - although you can use simple 23w cfls for cloners)
Also, if you buy that light, i would swap out two of the hot bulbs with two of the cold bulbs so you have a full spectrum.
*Edit* I didnt see you were only going to use it as a veg room, ignore the lower part, sorry....
something to think about though.
you have 28" vertically (lets say)
the light is about 3 1/2" thicks (lets say four inches)
a normal pot is about 8"tall
If i did simple math good enough, that tells me you have about 16" for plant growth.
While is possible to grow a normal strain, you will be doing alot of LST..... I reccomend a lowrydr/lowlife strain (such compact growth). You would be able to put more of them in the small area to maximize your yeild..
Just my .02 though..