A good quality core is more important than a massive intercooler. But just as important, is damming air to actually go through the intercooler. Air, like water, will follow the path of least resistance, so make sure its got good shrouding etc or it will just go around it.
Its not too hard to mount one, but make sure there is some sort of rubber or material between the two metals or it wont last long.
http://i173.photobucket.com/albums/w45/sco_aus/DSCF0006-1.jpg
Top radiator support mounts for the intercooler before shrouding.