You must already be knowing that that Intel Itanium architecture is different from Intel x86 architecture and even though Itanium remains in development and has reached a limited success in the niche of high end computing, it had been hoped to evolve into a replacement for lower end applications of the original x86 architecture.
One more interesting fact is that not every/all applications and OS works on IA-64 (Itanium) architecture and you might as well want to confirm this with VMWare if ESX 4 has been compiled to work on Itanium architecture.
As for the other family of server processors from Intel, the x86 based 64-bit Intel Xeon processors, I personally feel that it would be a lot easier and favorable for you to upgrade your existing hardware to Nehalem based Xeons processors since they not only support 64-Bit technology as their ancestors but also give you significant computing performance along with cut-down on your electricity costs and phenominal performance in virtualizion scenarios.
Most OSs' kernels today have been recompiled to support the latest Intel Nehalem architecture based 64-Bit Server/Desktop/Mobile CPUs and I would suggest that before you upgrade, you might want to scan the compatibility list for the OS.
Here is also a VMWare TCO/ROI Calculator (you might already be aware of it)
Hope this helps. In case of any further queries, you are always welcome to contact us.
Thank you, have a nice day!
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