Why GMA 4500M is so weak? It has everything you need like DX10 support, SM 4, the clock is about at 475MHZ. It supports Vertex and pixel shader as well, HW T&L too.
Even if you allocate some system memory to the X4500 accelerator, it just doesnt cut the mustard im afraid. Integrated graphics have never pleased me. They are ok if you are not running anything in need of graphics performance, otherwise its got to be a seperate gpu IMHO. Integrated are just a cheap solution.