The rockwork looks good, looks I like inspired you lol... See, its not that hard to turn alittle rock into something great.
Your LFS owner seems backward, did he try to push an undergravel filter on you too? LOL...
With T5HO's you want to make sure you get individual reflectors on all the bulbs, thats the biggest thing as whn you don't have these, the PAR output is about the same as power compacts.