For a higher-class DX10 card, a trusted brandname 400-500W PSU should do nicely. With Y2K's 10K budget, I'd agree with the C2D CPU + mobo, 2Gb DDR2-800, and probably an 8800GTS 320Mb, along with a new PSU. That will run current games very well. Then sell the GTS in 12 months, once the new DX10 hardware and software's been tested.
Whilst cheaper PSU's often do run well enough, it's wiser to ensure that new, higher-specced hardware is run off a reliable and guaranteed PSU.
Whilst cheaper PSU's often do run well enough, it's wiser to ensure that new, higher-specced hardware is run off a reliable and guaranteed PSU.