You could have that man if you wished very easily. I have room for 4 on my very low end case and i doubt SATA ports would be a limiting factor as you could just get an add on card and use a pci slot on your motherboard. Most motherboards have atleast 6 SATA connections anyway so 4 DVD drives + a couple of HDD's would be fine.
Though as wozza said you can't add more than 2 online, so you would have to call PCS anyway.
Yes I built one last week as we had a customer who contacted us and had requested that 4 dvd writer's be fitted into his case(CM690)and every single one of this sata's was used as he had a hard drive and his e-sata connected too!It's not to everyone's taste's as the customer did state that he would'nt be using all them all at once so I guess it was more for show!