What is the best substitute for Sharp 170W solar panel?

I'm pleased to inform you that substituting dissimilar modules of roughly equivalent voltages/amperages do not lead to substantial losses in performance.

Initially, it should be stated that "when two dissimilar modules are wired in series, the voltage is ... additive, but the current will be only slightly greater than the current produced by the panel with the lowest current output in the series string."  citation

The characteristics of your current modules, the Sharp NE-170C1, are as follows:

Vmp=34.8, Imp=4.9

The characteristics of our proposed alternative, the ET Solar ET-M572175, are as follows:

Vmp=36.24, Imp=4.83

Thus, as stated above, voltages will be additive while the current will trend down toward the lesser number. The trend down will be from 4.9 Amps to 4.83 Amps (in reality it would be somewhat higher than 4.83, but we'll go with the more conservative figure).

A string of 6 Sharp 170 modules would have an output of 1,023 watts ([6*34.8]*4.9).

If you were to expand your strings using two additional Sharp 170s, each string would have 1,364 watts ([8*34.8]*4.9).

By adding two of the proposed ET Solar 175 watt modules, each string would have 1,358 watts ([6*34.8+2*36.24]*4.83).

Therefore, in this instance your loss from mixing modules would be only 6 Watts.

I currently have a small installation of Sharp 170W panels.  I would like to expand my system but I am running into difficulties now that Sharp has discontinued all of their panels that are below 200 watts.  Is there a substitute solar panel with the same voltage at about the same cost per watt that I could add to my existing application without complications?  What would be the key factors to making this combined system achieve maximum performance? 

Well friend bit old question but were you able to find appropriate system? Even I have been searching for one for a while so can you solve my query?