I hear ya about saving money, but don’t throw good money after bad by buying used equipment that craps out on you, leaving you back at square 1.
I’d recommend you build one. Plan on no more than 35w/sqft absolute max output or about 300w. Color temp for the diodes would be dependent on what you’re using it for, but that’s not a big deal. Read this thread where I go into detail responding to similar questions:
And then follow the tips to do a bit of reading Cheap LED Strips : A Viable Alternative - #591 by nube and at the LEDGardener.com site.
As for the used SF-2000, I guess there’s a lotta ifs about used equipment. If you go that route, make sure you plug them in and let them run for 20+ minutes before you buy them. And try the dimming on both to make sure it works. And make sure there ain’t no dead diodes. And ask for proof of their date of purchase so you can figure out how long they’ve been used.