We bought one of these:
1 "Soleus Air CFM-25E 25-Pint Dehumidifier with Humidistat"
in Jan '08 for $150, and it's worked fine. I don't like the company, and it isn't energy-star rated, but I have to admit that it's done it's job quietly and reliably.
We also got a Kenmore at a garage sale for $20. It also works well and has a reservoir that's easier to remove, although it's louder.
The Soleus keeps the fan on even when the humidity is below the set point, the Kenmore does not (preferred). Also, the Soleus won't restart if the power goes out momentarily, meaning you can't have it on a timer.
Remember that a stronger unit won't necessarily use much more energy since it will presumably be on less.