Recently Nvidia released their GTX550 Ti graphics cards to add to the 500 series of cards. This new card is meant to be the replacement for the GTS450 with a price point around $135, however since this is a factory overclocked card with an upgraded cooler, this particular model has a price of $154.99. These numbers are before any mail-in rebates that are offered. The base MSRP of the GTX550 is right around $20 more than that the GTS450.
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips