  Current expectations on the signal to noise ratios and masses of supermassive
black holes which the Laser Interferometer Space Antenna (LISA) can observe are
based on using in matched filtering only the dominant harmonic of the inspiral
waveform at twice the orbital frequency. Other harmonics will affect the
signal-to-noise ratio of systems currently believed to be observable by LISA.
More significantly, inclusion of other harmonics in our matched filters would
mean that more massive systems that were previously thought to be {\it not}
visible in LISA should be detectable with reasonable SNRs. Our estimates show
that we should be able to significantly increase the mass reach of LISA and
observe the more commonly occurring supermassive black holes of masses $\sim
10^8M_\odot.$ More specifically, with the inclusion of all known harmonics LISA
will be able to observe even supermassive black hole coalescences with total
mass $\sim 10^8 M_\odot (10^9M_\odot)$ (and mass-ratio 0.1) for a low frequency
cut-off of $10^{-4}{\rm Hz}$ $(10^{-5}{\rm Hz})$ with an SNR up to $\sim 60$
$(\sim 30)$ at a distance of 3 Gpc. This is important from the astrophysical
viewpoint since observational evidence for the existence of black holes in this
mass range is quite strong and binaries containing such supermassive black
holes will be inaccessible to LISA if one uses as detection templates only the
dominant harmonic.
