I bought a drum carder (Ashford) some years ago, but I don't find it particularly speeds things up, or at least not as much as I had hoped. I also tried sending off some fleeces to be commercially carded, in the hope that that would speed up matters, but I wasn't happy with the result - the carded fleece (Shetland) was full of noils. Can you spin any of your fleeces without carding? Do you have a flick carder to separate the tips and butts. Often Shetland can be spun without carding.
With the Ashford carder, I have to put the fleece through at least twice, then I tear the batt up into little pieces and make rolags - maybe I'm not using it efficiently. I don't have any extras with it, just the doffing spike, which I also use to clean the tines.
I will be interested to hear what others think of other makes of carder - I bought the Ashford because that was what was available at the time.