The Greenstar does a great job GRINDING greens, but not such a great job juicing them because it foams them too much. So to do a great job with greens you'll want the Greenstar to grind them and a press to press them. The Wells Press may be more money than you'd like to spend, but there's been some interesting discussion in another juicing group about saving money on a press by buying a 6-ton hydraulic shop press at Harbor Freight for just $59.00 http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=1666, and improvising the juice trays. You can actually buy the stainless steel Norwalk juice tray for a measly $37.00. That gives you a super-powerful press for under $100.00.
That way you'd have the ultimate high-quality juicing set-up -- a Champion to grind carrots and other "hard" vegetables, a Greenstar to grind wheatgrass and green leafy's, and a press far more powerful than you'll ever need.
Another solution would be to buy a single-screw juicer such as a Samson. They do an excellent job with wheatgrass and green leafy's, and they're a snap to clean. But they're plastic and kind of flimsy.