We study high-order harmonic generation (HHG) driven by seeded plasmonically enhanced fields. On one hand, plasmonically enhanced fields have shown a great potential to extend the HHG cutoff, an instrumental prerequisite for the generation of attosecond pulses. On another hand, the use of XUV seeds appears to have a considerable potential to improve the HHG conversion efficiency, which is typically modest when a unique fundamental laser pulse is employed. By mixing these two sources, we show it is possible to simultaneously boost the HHG cutoff and to increase the harmonic photon flux. The combination of these features potentially enables one to generate intense and spectrally broad attosecond pulse trains.