the A10-5800 is a much better cpu than either celeron, its built in GPU is better than the 640, but not as good as the 450. The celerons woud hold the 450 back enough to make the A10 competitive. for a $300-350 total system, the A10 s the very best chip
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If you cant afford 1866, use 1600, it only loses 2-3 fps compared to 1866.