The differences between expensive models and bottom of the line are not that big to my ears. A Stereophile author admitted as much a few years ago.
That said, SACD can sound MUCH better than a Red Book CD. I've got a Oppo DV-890H, a Sony DVP-9100ES, Sony DVP-9000ES, and Sony DVP-NC-555ES, and Sony SCD-C2000ES - they all sound pretty much the same on CDs and on SACD.
Getting a model that handles HDCD is a big plus to my mind. I put on a Grateful Dead CD once and as it started to play, I said to myself "Darn, that sound really good!" Turns out it was encoded in HDCD.
Also, check human factors of the operating controls and the availability of replacement lasers. Some can be a bear to operate without a remote and lasers do go bad over the years.