We theoretically study a novel approach for soliton-induced high-power supercontinuum generation by using kagome lattice HC-PCFs filled with a noble gas. Anomalous dispersion and broad-band low loss of these fibers enable the generation of two-octave broad spectra by fs pulses, with high coherence and high spectral peak power densities up to five orders of magnitude larger than in standard PCFs. In addition, up to 20% of the output radiation energy forms a narrow UV/VUV band, which can be tuned by controlling the pressure in the range from 350 nm to 120 nm. In the temporal domain this corresponds to sub-10-fs UV/VUV pulses with pulse energy of few tens of microJ, caused by the formation of a high-order soliton emitting non-solitonic radiation.