This could be done with smart objects, and fortunately Photoshop CS3 does have that feature. Load up the proxy version in CS3, convert that layer to a SO. Then apply the effects. Save, and open the file on your mean machine – and replace the SO content with the new high-res version.
Actual destructive effects will NOT work, though.
In that case you might also wish to try setting up an action that repeats the same steps – although certain filter settings would affect the higher resolution version in a different manner.
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System: Win7 64bit – i7 920@3.6Ghz, p6t Deluxe v1, 48gb (6x8gb RipjawsX), ATI 7970 3gb, EVGA 590 3GB, Revodrive X2 240gb, e-mu 1820. Screens: 2 x Samsung s27a850ds 2560×1440, HP 1920×1200 in portrait mode