If those specs are true it looks like the GTS 450 will basically replace the GTS 250 in price point with around GTX 260 performance, not bad. Though I hope it won't be too far behind the GTX 260 due to the 128-bit bus. That may cripple it. They bemoan the TDP but it's actually lower than the GTS 250 (at 150 w) but yes a little bit higher than the 5770, but hopefully it performs better than the 5770.
These should be very good cards for physx btw.