planetaquariums.com I know you said Cheap, but I'd like to point out, you're putting hundreds, if not thousands of dollars worth of corals and fish into that Tank, why cheap out and buy something of low quality or workmanship?
PA is 2 guys, a Master Designer and a Master Builder from OCEANIC!! If you're anything like me you know of, and LOVE The Oceanic Brand, I have owned several, a 125g, a 180g, 90G bowfront and my Pride and JOY, 8foot 300g I have now.
If it was me, and I was looking at a 75 upgrade to a 55g, I'd probably take another step up into a 120g 4foot tank. Same footprint as the 75 basically but stepping into a 120g opens up options for TANG's you do not have in a 55g or a 75g.
Another option is to buy a 75g Aqueon. I have had several of these tanks, I have one set up for QT right now and you can buy them for about $120 if you watch for the Petco Sale. Easily the most affordable 75g option there is!!
DO NOT...I REPEAT DO NOT!! Buy a Red Sea unless you spend a few days researching Red Sea Fails.
Good Luck in whatever ya decide.