Yes they are 'regular' RCA outs like on consumer level audio gear.
Essentially, the US-122 only has unbalanced outputs.... Without getting into too much technical detail, that basically means you have some signal and cable length restrictions and are not provided with the same interference protection as you do with a balanced signal (there's more to it than that of course, but you get the idea).
Your KRK's will accept balanced input, so if you do decide to upgrade from the US-122, they will compensate.
I keep a US-122 in my Laptop case for a quick and dirty way to nab some basic remote recordings... Phantom power and fully USB reliant, it does well for what I usually need it to do. Although, I think the USB is only 1.1
As far as a sole interface for any serious down and dirty sessions, you can do better for relatively cheap. (I picked up a Mackie Satellite for under $100 that I'm pretty happy with for remote stuff as well). Other folks will probably chime in on inexpensive solutions that work well for them as well (M-Audio, Presonus, MOTU, etc.)
Hope this helps!