Performance at default settings How do these motherboards perform when everything set to default speed? The past has told us great overclocking boards generally perform mediocre at default speed, insuring some headroom for overclocking.
Synthetic performance (Futuremark):

The Asus K8N-E is the undisputable leader when everything is set to default. Looks like Asus has done some tweaking to make sure their motherboard was the fastest NForce3 250Gb board out-of-the-box. The MSI performs like most NF3 motherboards, while the DFI is a tad slower. That's the downside if you want to design a great overclocking board, it won't be the fastest when run at stock speeds.
The Abit K8T800 Pro falls a little behind too, but the results are still respectable. The difference is too small to notice in real life.
High end gaming performance (Doom 3):

The differences in Doom 3 are even bigger, the Asus K8N-E is an astonishing 10% faster than the DFI NF3 250Gb.
Calculational Power (PiFast):

Once more, the Asus K8N-E takes the lead. The un-tweaked DFI manages to put down a healthy result when it comes to raw calculation power. The Abit K8T800 Pro once more doesn't manage to keep up with the NF3 motherboards, but the difference isn't too huge to ditch your current K8T800 based motherboard for a NF3 one.
Synthetic memory Performance (Sisoft Sandra):

A purely theoretic benchmark, but useful as a reference none the less. The Abit K8T800 Pro is just a tad slower when it comes to memory performance.
HD Controller:

Although the Abit K8T800 Pro only offers two S-ATA connections, their performance is on par with NVIDIA's solution. All motherboards showed a 2% CPU load during the tests.