In addtion I would beef up the RAM from 24 to at least 32GB especially if you are going to go with HA/DRS and you only have two servers.. Exchange and SQL can be some big memory consumers and you would want the ability to take a single host failure.

Memory will always be your bottleneck in the virtual space.

The IBM solution with the S chassis is a good bet if you would like to use their integrated storage for shared storage accross you ESX servers.. And the HS22 max memory is at 96GB last I checked. I would get as close to the sweet spot on memory as possible with your solution which woudl probably be filing up all slots with 4GB DIMMs. As far as the S chassis from IBM it is designed for the exact purpose you are looking at.

Hope that helps.

Help me help you by scoring points.

1. I agree with the memory comments, except that nehalems require you to stay in groups of 6 for best performance. Being 12 DIMMs will slow down the memory speed of the2.66 GHz E5550 processor. I would suggest 12x4G DIMMs for the best price performance, giving you 48G, and dropping down to the 2.53GHz E5540 processor; which will match the memory speed and save some money. The memory for cpu trade off is well worth it. http://www.intel.com/p/en_US/products/server/processor/xeon5000/specifications

2. Don't forget Fujitsu. They have a solid product line and decent support. With all servers being servers, choose the vendor you feel you will get the best support out of.

3. You don't necessarilly need a SAN. You just need shared storage. I use a NetApp filer and run my vms over NFS. It is an inexpensive way to have shared storage and not have to foot the bill for FC. Anyone that says that NFS does not scale or perform can come see my 500+ production guests running on IBM x3850s backed by a NetApp filer. I also run approximately 500 more VMs over FC and iSCSI, so I am intimately familiar with the differences. The value add of NFS, especially for a small shop, is very good. Dedup mixed with the Rapid Cloning Utility means that I can run these VMs thin provisioned on my storage without giving VMware any more of my money. Snap Drive for VMware lets me take hot backups of my VMs and mirror them to a DR site without having to deal with vmwares snapshot implementation; which eats disk space.

4. If you decide to go with 10G networking, get an Intel NIC. I don't care what server you buy. VMware has the best support for Intel. They know Intel. They even hint at Intel in their docs. (No, I don't work for Intel. You can guess who I work for by reading comment 3.)

I would look carefully at the option with the MD3000i, we have one which was use as "dumb as rocks" shared storage because that's what it is, dumb as rocks compared to something such as the VSA or Equallogic boxes.