  The main result of the paper is a natural construction of the spherical
subalgebra in a symplectic reflection algebra associated with a wreath-product
in terms of quantum hamiltonian reduction of an algebra of differential
operators on a representation space of an extended Dynkin quiver. The existence
of such a construction has been conjectured in [EG].
  We also present a new approach to reflection functors and shift functors for
generalized preprojective algebras and symplectic reflection algebras
associated with wreath-products.
