The Weiand Stealth and the Summit Stage 2 are the exact same manifold. Weiand must make the Stage 2 for Summit so they can use it under their brand name, they are totally identical in every way.
The real question than is between the Stealth and the X-Celerator. The Stealth is a dual plane intake good till about 6500rpm, and the X-Celerator is a single plane intake with a different powerband that starts later but goes until 7000+rpm.
If you plan on driving on the street mostly and only occasionally racing at the drag strip, either the Weiand Stealth or the Edelbrock RPM Air-Gap will be your best choice because of their street friendly rpm range and outstanding low end torque.
If you plan on racing more than street driving, forget the X-Celerator and look at the Edelbrock Victor Jr. single plane intake. The Victor Jr. makes a lot more top end power than the X-Celerator, but neither the X-Celerator or Victor Jr. is optimum for street driving because of their higher rpm range and loss of low end torque.