Welcome to APC
I also come form a reef background. You have a tank there that can really a good bit of fun. You don't need to lose the sump. I have one on my 120, yeah I use a bit of CO2 but I like having a sump. great place to stash the heater, probes and run a closed loop for CO2 and UV. Filtration wise you don't much much and the plants do a lot, just a sponge in the sump to pull out some of the junk.
Light wise being it's a 6' tank I'd drop the 250 to 175 and use all three with 6500 - 10k bulbs.
However, before you do any hardware changes, what are your goals with the tank?