definetly talk to Carl, the man has made very nice tapes with both pres. I have very limited experience with the 248, it's a fine piece of gear though... I think with 480's I'd break towards the m148 but I like coloration. The m148 is pretty clean, not quite as clean as a V2 but pretty clean, with just the right amount of lowened coloration to make me happy. My favorite combo thus far is m148->V3.
One other thing is that Doug no longer makes the m248, in fact I don't think he's built them since early 2002, but you can still get an m148 brand new (though there is a several month wait as Doug hand builds them all).
You can't go wrong with either but they are definitely two distinct flavors.