On the subject of the extra depth of flavour found in restaurant curries (without using whole spices), and another thread here about a mystery 'anise' background in restaurant curries, there is a video on CBM Mick's blog where a chef sprinkles on his own home made garam masala towards the end of the cooking of a jalfrezi. It turns out this is not a blend, but simply dried and ground Indian star anise. He does seem to put on a fair bit too. I haven't tried this, but this does point towards the garam masala as being the secret.