I have the 4ft Infiniti over my tank. I also have a 6ft Spectra. I took the Spectra down to experiment with another setup. Im using a 4ft Infiniti coupled with two Radion Pros on either side. My tank is a Reef Savvy Rimless 250 gallon. I think the Infiniti provides more than enough coverage on a tank 20-22 inches in depth and 30 inches or less in width. The single ended Spectra, however would be better in a deeper tank depth of 30 inches or deeper with a tank width of greater than 30 inches.
I have the Luxcore performance series Electronic Ballasts, fast start up, low heat, and dead silent. They're anodized extruded aluminum and have a selectable wattage. I love these ballasts and have been awesome and definitely worth the money.
I have a rimless as well and my tank hasn't overheated with either fixture. My water stays around 78-80 degrees year around. I do however live in Idaho where the summers are hot and winters are cold. Never had an issue with heat transfer because my AC unit keeps my house @ 74 degrees in the summer. I also think the rimless tanks keep the heat transfer down a lot more and help significantly.
I like the fact of running the best of all worlds. T5's, metal halides, and LED's. I ended up buying Jellymon's Infiniti that he posted a few pages back with the Reef Savvy 120 gallon. I got lucky and bought his entire setup from him as he decided to go to another Project.
Thanks Jellymon for the tank setup. Its awesome.! I hope your Impala works out.