Stereo Imaging ?

Pan tracks harder.

This may be a bit obvious but have you made sure that you have panned the instruments off to the sides that they should be on.. eg, left O'head panned left with the hats (from drummers perspective) I have heard may recording where to overheads are panned opposite to them selves resulting in a very narrow drum sound. Check you panning on the individual tracks and also make sure that any Aux/buss sends are also panned to same direction, you could even try panning them wider for the sends so that ant FX such as reverb don't Mono-ise them so much. Check for Phase/Polartity problems as this will lead to cancellation of frequencies although phase is what stereo enhancers use to add that stereo depth... The plug in to try is the Waves S1 or imager....(used on a drum submix) but you should be able to get quite a wide spread from EQ Balance and Panning...

Waves has a plugin that can do this...i've played with it once before. It's called the S1 Stereo Imager. Poke around on their website and you should be able to find it.

Once I recorded a drum kit with alot of toms, and they were played in big rolls up and down. We didn't have enough channels at the time to record each individual tom, but when we heard a big drum fill on the toms, we automated the panning such that when the drummer hit the highest tom, the tom mics were panned hard left, and when the drummer hit the next tom, the panning was slightly more right, and so on. The drum fills sounded nice and big that way, for what it's worth.

Obviously this may have to do with your overhead placement. What configuration did you use?