The South Beach hotel scene is insanely overpriced and nearly all of them need a good cleaning/renovation/rehab. I'm always marvel at how disappointing Miami's 'top tier' properties are with ridiculously low levels of service.
Look at Downtown, Miami Beach (much cheaper) and Brickell (super new oceanfront condos, great prices).
If you must be in South Beach, look at Airbnb or HomeAway. Much better options, more space and a wider price point.