The stringent distance dependence of Forster resonance energy transfer (FRET) has limited the ability of an energy donor to donate excitation energy to an acceptor over a Forster critical distance (R-0) of 2-6 nm. This poses a fundamental size constraint (<8 nm or similar to 4R(0)) for experimentation requiring particle-based energy donors. Here, we describe a spatial distribution function model and theoretically validate that the particle size constraint can be mitigated through coupling FRET with a resonant energy migration process. By combining excitation energy migration and surface trapping, we demonstrate experimentally an over 600-fold enhancement over acceptor emission for large nanocrystals (30 nm or similar to 15R(0)) with surface-anchored molecular acceptors. Our work shows that the migration-coupled approach can dramatically improve sensitivity in FRET-limited measurement, with potential applications ranging from facile photochemical synthesis to biological sensing and imaging at the single-molecule level.