Oh man, im sure this thread could go into 2015! Anyways, my 2 pennies,
I feel there's almost no rules these days as to what you can do-like others said, it all depends on what you want out of your rig and what you want to do w/it.Pull up a diagram of almost every single professional touring musicians's rig and you'll more than not, find a combination of rack gear and pedals.All mixed in together-one way or another....
I like a combination of both, for instance: Im forever in love w/ 2290 for amazing chorus and delays.I dig the noise reduction in rack gear,Love the Eventide H-7600,etc too...but Im always diggin the overdrive of pedals like,the wampler paisley drive,xotic pedals,octavers,phasers, and wah pedals....and nowadays youve got all the killer rack interfaces and pedal loopers to pull this off quite easily!