The cheapest way of improving sales is probably to just bundle some first-party software with the different SKUs. Maybe Uncharted 2 and Killzone 2 160GB bundle, Modnation Racers and LittleBigPlanet 160GB bundle, God of War 3 and Infamous 160GB bundle. Maybe GoW3 should be switched for something else, as it is the first holiday season for the game and should sell fine on its own (the same for Modnation, but it isn't exactly lighting up the charts so it could use a bundle). The cost of first-party games should be peanuts to bundle.
Bundling Move at $299 could be very effective, but it would be more costly than bundling first-party games (I'm assuming the hardware is more expensive than packing in first-party games with the console). Obviously, 3rd party software would be more expensive than 1st party, but Sony have a strong enough first party to offer a nice variety of bundles with just their own software.
The most expensive method of driving sales is almost certainly a price cut, but it would need to be $50 to be truly effective, and I just don't think that is something Sony should be pushing (maybe in EU where the PS3 is €299, which is almost ~$400 at current exchange rates).
