I got a price of $550 to do my ramp with armorthane(just like rhino lining). it a little larger than yours. IMO, $$ was kind of steep for our applicaitons.
you can get herculiner DIY liners from JC Whitney. its 100$ a gallon and you could get one application out of it. Its used on the floor of jeep wranglers, not as tough as rhino.
http://www.jcwhitney.com/autoparts/...Id-100000283140/Pr-p_CATENTRY_ID:100000283140
steer clear of the diamond plate.
Looks good, but when it gets wet, greasy, or worse, both, you have a real problem.
the rest of us will most likely just watch and laugh(aftrer we made sure you didnt get hurt).
All i all, i liked the epoxy paint becase i can recoat when it gets too nasty. it scrubs well, but eventually the grease stains dont come out. It usually gets a new coat in the beginning and then halfway thru the season depending on how much crap sledneck spills on it.