Unless you're going to expand to 48" I wouldn't bother to upgrade.
You can buy 3 48" LET kits and make a hollow frame from wood from home depot and will cost about $350 total. This fixture is light and will hang from your current light hooks.
LET reflectors are wide and have the same coverage as a 8 bulb Sunpower.
Going this route also gives you options to add/mix in some LED bars in the future. Make sure you make the frame 24x48 or even slightly bigger by an inch all around.