We sell both as well. I guese the I would ask what is the application? Large call volume small call volume? Aspire S is a definate NO NO for you if you plan to goto 40 phones as well as the E class ESI. You plan on PRI/T1 or copper? ACD? Large auto attendant usage?

I would differ from Bill in the fact I see ESI being around a long time. They actually make componants and voicemails for other large phone companies as well as have their own patented chipset.