I personally never recommend "square footprint" lights for rectangular shallow tanks.. You'd need 2 Kessils for coverage.
'If" you want to spend that kind of money.. The Current plus pro is "Arguably" the most flexible choice.
The Beamswork "may" be a minor light downgrade from 2 "efficient" t5's (but an upgrade from non-efficent ones) but the spectrum quality is good (well a close-ish match to what you are currently running) and probably a bit more suited to low tech..
you still will have close to 80PAR at 12"
This is a "double" of the Beamswork.. Dividing PAR by 2 gives a rough estimate:
It is no secret that I'm not a "fan" of Kessils due to the lack of information on spectrum and PAR from the manuf..Something I can tolerate in "cheaper" products but not "high end".........
Note: You could do one Kessil raised up to cover the 30" length but then you have a 30" width.. LOT of light spill..