RHEL 5 32 bit hardware compatibility

If you read the product comparison at http://www.redhat.com/rhel/compare/, you will see the following note.

[1] Red Hat defines physical CPUs equivalently to sockets, so a multi-core and/or hyperthreading CPU is counted as a single socket when determining which subscription to purchase

On the same page it notes:
[4] Red Hat defines a logical CPU as any schedulable entity. So every core/thread in a multi-core/thread processor is a logical CPU

So what this means is that with your dual quad-core system you will be running 8 logical processors, the x86 (32-bit) version can handle up to 32 logical processors.

However I would recommend looking at using the AMD64/Intel64 verison which would better utilize the multi-core processors you have installed.