If you're going to invest in a hood like that I think you're better off getting the T5 version and use the 5.0 bulb (6-8'' optimal distance) so that you can upgrade later to a 10.0 (10-14'' optimal distance) and not have to buy a new fixture. The T8 will top out at the equivalent (ish) output of the T5 5.0.
Are you still using the 100w PowerSun? That should be producing a good amount of UVB at 10-12''. The downside is just that it's difficult to control the heat when you have the bulb fixed at that distance for UVB output. If you can maintain 103 basking surface temps with the combination of bulbs and the PowerSun is at 10-12'' above the main basking area I think that should work for now.
If you do decide to move to a separate UVB fixture, you can move the PowerSun into a portable dome fixture and use it as a basking spot for outside the tank and for travel.
Are you still using the 100w PowerSun? That should be producing a good amount of UVB at 10-12''. The downside is just that it's difficult to control the heat when you have the bulb fixed at that distance for UVB output. If you can maintain 103 basking surface temps with the combination of bulbs and the PowerSun is at 10-12'' above the main basking area I think that should work for now.
If you do decide to move to a separate UVB fixture, you can move the PowerSun into a portable dome fixture and use it as a basking spot for outside the tank and for travel.