i know this is now well off thread, but just to jump in on Armistace's bypassing the pre's using half jacking; if you want to guarantee that it'll work/don't fancy fiddling with making sure the jack is only half in, just using a standard "insert Y cable" and just using the return jack (sleeve) from the output of the external pre/channel strip. it may cost a little more than a standard jack cable but does mean you don't run the risk of knocking the cable out/extra fiddling.
We've been doing this at work for a long time now through a patch bay which has the sends and returns from the inserts on it. i don't have anything against the pre's on the desk (Soundcraft Ghost) but they sound quite boring imo