I have the 'old' version the DUo Deep 800.
Good value tank and the lights are OK. I ended up modding mine right up and have since remodded them back down.
Buy some decent polished metal reflectors (£5 each from P@H) and some decent tubes to replace the dodgy hagen ones supplied with the tank and it is OK for plants.
No need to up the lights really or you'll be end up needing dosing regimes and CO2 (which I do)
I have also replaced the filter as I wanted a larger cannister and not an internal. I also replaced the heater to an external more due to aesthetics as the tronics supplied are quite good.
So just need to buy the reflectors which can clip onto your existing tubes and then upgrade the tubes. The Arcadia ones that P@H sell are a decent starting point and IMO the freshwater (green box don't know what its called in P@H as they have them renamed for some reason) is one of the best colour renditions out ther and I still use one to this day. Mix one of these with a tropical pink light (the pink box. again don't know what its called in P@H) and it should balance the colour nicely.
Take a look at barrreport.com at non CO2 methods which are aimed at low-medium light tanks and will give you a good idea of what to start off with rather than having to change substrates etc later on.
This is how my Fluval Duo Deep 800 (125Ltr) looks these days. Loads of unnecessary mods etc. lol
Andy