Now that GRT has turned up the engine monitor feature set in their Mini EFIS product, I would highly recommend the Mini. Go for the Mini-X and you'll have a complete, stand-alone EFIS system which will also display engine parameters.
The Grand Rapids Mini features a very bright, crisp display, is light, consumes little power, and will easily fit in the VM1000 hole. I'm trying to convince my hangar-mate to do this very same swap in his RV-8A.