If you like the way your existing marineland light looks why not just keep it and do a DIY LED add on? You could add a fixture with some true violets pretty easy, they wouldnt change the look of the tank much, except make the corals pop a bit more.
True Violets are $5.50 each on rapidled, 14 led drivers are $16 each.
Stevesleds has cooling fans for $16 each and matching 20" tube heatsinks for $6 each.
Assuming you have a 20 gallon long that is 30" x 12" you are looking at 360 square inches. "High light" for LEDs is usually considered 1 3 watt LED per 15 square inches of tank surface area (360/15 = 24 LEDs) up to 24" deep, medium is 1 3 watt LED per 20 square inches (360/20 = 18).
So assuming you bought 24 violet LEDs + 2 drivers from rapidled and 2 fans+2 heatsinks from stevesleds (although I think one of each would suffice) = $108+$32+$32+$12 = $184, you would still have to get some wire, solder, thermal adhesive but you would stay way under your $300 budget and have a bad *** looking 20 gallon tank with plenty of lighting for any corals.
Just a thought.