Xen users - May 2012 - Intel Xeon Question

Hello Experts,

I have now gotten some IBM eServer xSeries 345 with Intel Xeon 604 (32bit)
CPUs from 2.0-3.2 Ghz and 4 and 8 GByte of memory.

I like to run only Debian 6.0 on itike to know, whether I can

1)  Run only am singel 3.2 Ghz CPU with 4 or 8 GByte of memory
    (each domU need only 256 to 1045 GByte of memory)

or is it better to run

2)  two smaller 2.0-2.4 GHz CPUs?

Note:   In case of power consumation it does not mather whether the x345
        run a singel 3.2 Ghz CPU or two 2.0 Ghz CPUs because it consum
        always 275 Watt with 8 GByte of memory and 6 SCSI dived of 147 GB

Thanks
Kalham