Bass/Larger Speaker Options for XDJ-RX

Hi Folks, I have a pair of KRK Rokit 5 monitors that I use and perfect for home DJing. However, I've been asked to DJ at a couple of gigs and will need to bring my own audio equipment. Can anyone recommend any solid but not too expensive sub woofers/larger speakers considering my current setup with my KRKs? Thanks in advance all!