I highly recommend buying a machine with a true "DSP" controller like one from Ruida. The Ruida controller uses software called RDWorks/Laserworks. The Ruida control panel typically looks like this:
RuiDa RDC6442G CO2 Laser Cutting Engraving DSP Controller System | eBay
RDWorks/Laserworks lets you set different elements different colors/layers. Each color/layer can be set to either engrave or cut (at different powers/speed).
There is a great new user group for users of the RDWorks/Laserworks software at rdworkslab dot com.
If you are going to be using your laser for long periods of time (hours per day), or your ambient temperature is high, then I would highly recommend a chiller to extend the life of your laser tube. Different manufacturers have various recommendations, but generally the cooler you can keep the laser tube the longer the life. I keep my chiller at 19 degrees C for a 50W laser. Before I had a chiller the water temp would go up to 30C pretty quickly, especially during the summer, which is not good for long tube life. Beware, the cheaper chillers (e.g. the CW3000) are actually just radiators and can only get the water temperature down to ambient. Chillers like the CW5000 and the ones on Lightobject dot com are actual chillers (i.e. they contain refrigerant and keep the water at the temperature you set).
I wouldn't worry about the rotary attachment unless you definitely have a use for it. I have never used mine. I am sure you could buy one separately if you do start to have a need for it.