the 1604 is a dear mixer to buy new, if u look hard u can pick a second hand one up quite cheap, i got one a couple of months ago to seperate my 909 sounds out. I payed £380 for mine, it was a year old and in reallly good nick.
look on www.soundonsound.com in the readers ads (thats where i found mine) or on www.loot.com
;)