Performance and Load Balancing in Dual Athlon Kernels?

How are processes, and multiple threads of a single process, balanced accross multiple processors?

part of the motivation is to determine what will run faster... Dual Athlon 2400 with PC2100 memory - 760MPX Chips
OR
Single Athlon 2400 with PC2700/3200 - KT400 Chips

There dont seem to be any boards for dual Athlon and the faster RAM.

some of the boards I am looking at are below. Any specific comments are welcome.

Dual Athlon 2400MP and PC2100 - 760MPX
<MPX only supports PC2100>
Motherboards considered

    ASUS A7M266-D
    Tyan Thunder K7X (S2468)
    MSI K7D Master (MS-6501-030)
    Gigabyte GA7DPXDW+
    Gigabyte GA7DPDW-C

        VS

Single Athlon and PC2700 or PC3200 - KT400
<No motherboards found w/ fast RAM and dual cpu>
ASUS A7V8X LAN
Soyo SY-KT400 DRAGON Ultra
Soyo SY-KT400 DRAGON Ultra (Platinum Edition)
Gigabyte GA-7VAXP Ultra

nForce2

    ASUS A7N8X - PC3200/2700

Thanks.