I have no info on e-counters.com, but did recently install Silestone in our kitchen redo. (Which BTW we absolutely love).
I ended up going thru HD for the countertop, they provided the lowest bid. The contractor that did perform the installation, had also independently bid the same job and came in over $500 over the HD quote. The only thing I could figure was that HD provides enough business for this firm that they get a lower rate. The installing company did mention (during the installation) that they were currently installing over 30 countertops a week...
I did get the impression from any installer that the 'advertised' price was simply to get you in the door. Once in, all the 'extras' (upgrade edge treatment, sink cut-outs, etc.) drove the final cost upward...
BTW we ended up paying nearly $80SF installed (total cost / SF). This is nearly double the 'advertised' cost per SF....
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Good luck!
Rick