There are quite a few options to get you into the qualifying tax credit systems, most are using two stage compressors. However, there are several brands that will get you there more economically by using a 14 SEER condenser and an air handler with an ECM motor (not variable speed). Check into these options with YORK in the YHJF series heat pumps and Several lines from ICP (Comfortmaker, Tempstar, etc.). I have found these to be in that "sweet spot" for consumers: getting the tax credit for efficiency and not breaking the bank on the initial installation.
You can't learn a thing with your mouth open.