i'm using a pair of audioengine a5+ powered speakers with my imac- adding a sub soon.
thanks in advance for any help!
With a USB DAC, yes: Just connect the DAC to a (powered) USB port. If it didn't come with cables, buy something inexpensive, but reliable, from a company like Monoprice.
Cables for home audio aren't an investment; they're another expense. Overpriced, brand-name cables (interconnect, power, USB, HDMI, or anything else) are designed specifically and solely to improve the profit margins of the manufacturers. A9X-308 get it exactly right when he says, "As soon as you start to read flowery prose describing purported cable 'sonic' attributes, especially if they are expensive, move on."
Personally, I own a number of Monster cables, all of which I bought at significant discounts through third-party sellers on Amazon. They're nicely constructed. They don't improve the audio. My friends aren't impressed with my refined tastes. But I like them anyway.