Yeh I was thinking low tech as I'm just starting out , with easy plants for the same reason, I have no real idea of budget, but I have kept a reef tank in the past so know things can add up !
Giesemann gets my vote
Dimmable would be fantastic but significantly increases cost
If you do bring in the Razor T5 system, I’d just order the T5’s as well - they are outstanding lamps in both intensity and color rendition - 2 sets of tubes should last 4-5 years: fluorescent spectra does degrade over time, as does light output which is why some suggest annual replacement; if you wait 2-3 years, then make sure you transition aquarium to the “new” lighting
Unfortunately the 30 inch height + 24 inch back to front, isn’t the most economic footprint to light effectively, I’d want 3-4 T5’s for more uniform light distribution front to back or combination of T5 and LED or LED (most expensive initial outlay)
Green Aqua offers (several display tanks run on the ATI’s) ATI luminaries, including dimmable and non dimmable 80w versions in 4, 6 & 8 lamps (I prefer the Giesemann T5 options over those carried by GA)
The 8 would give you the best light distribution across the 60cm front to back width of tank, but would be far too much light for low tech, depending on how the system is configured you may be able to run the lamps in various configurations (or this may be very limited) so ask how many lamps/power switch, and can you remove lamps etc
eg I have an older T5 luminaire with 4 x T5, with lamps 1&3, and 2&4 on separate switches, removing 1 T5 will shut down that ballast, so I can only choose 2 or 4 lamp configuration
Being able to raise/lower the luminaire will increase options in light distribution and intensity, so pendant style would be my vote
(the luminaire dimensions are a reasonable estimate of T5 spread)
If you look at Filipe Oliveira’s Youtube channel, he has several examples of 70 - 90cm tall tanks, including one long term Aquaflora display aquarium which has gone through the transition from T5 to LED (growth improved)
Depending on local costs, Prime Freshwater HD may an option, each will “light” a 45cm cube with moderate to high PAR (depending) - FO uses these with excellent results even on deeper tanks (I don’t recall the other LEDs used on the deeper display tanks)
Obviously Kessil A360X (tuna sun) would be an option but also may be most expensive, I’d begin with 3, though if you want to do island scapes, 2 would suffice (and it’s very easy to add a third)
These style of LED will give you the most versatile and cleanest profile for lights
It’s well worth a road trip to see the various light options in person
As you surmise, current lights won’t deliver much substrate PAR (I suspect not even “low”)