I have been playing Live from the earlier model electribes (own the ER, EA & ES) for the past 4 years.

I concur with what Komplex said.

I will add that the ER-1 is pretty weak by itself and requires a good comp/lim to get some guts out of it. Probably better not getting it at all and go for the EMX. If you get the EMX you wouldnt need the ER or the EA.

I just bought the ESX-1 and am gobsmacked by its playability and improvements over the older models. Absolute solid sound quality and flexibility.

I plan to get the EMX soon and then I will just do my live set from the ESX & EMX only. Thats plenty of room for a solid Live Techno set from just two machines and a mixer.