Depends on what you regard as "easy".
An add-on PCI card will add another two controllers, for as many as 4
additional devices. I used to use a Promise Ultra 100 TX2 card, which is an
old product, but still available. With sufficiently recent firmware, the
card supports LBA48 drives (larger than 137 MB). I never tried it with
removable devices, like optical drives, but I have read claims that it
doesn't work well with them. It's easy enough to keep all the opticals on
the mainboard's controllers.
http://www.newegg.com/Product/Product.asp?Item=N82E16816102002
It needs one IRQ.