Spots Available on Cruises this Austral Summer?

We just decided last week that there isn't any other place that we'd really like to see apart from Antartica. But it is already mid-Oct. Are there spots still available in any of the cruises headed out to Antartica in Dec, Jan or Feb? Do we have to pay a premium for booking so late?

One other thing, how do we choose from the myriad companies that offer cruises? Does any one have any recommendation, which operators I should enquire with for what would probably be my first and only time visiting Antartica?

Hope that there are some of you out there with good suggestions.