Cisco doesn't try to push folks to use one platform or another. We just require that it has been qualified.
The ICS is a special platform with special Unity licensing. For some customers the ICS, which can support CM and Unity in a single box, is more cost effective.
At this time we aren't supporting and as of a couple weeks ago we didnt have plans to support the Dell blade servers. You should contact your sales team if support is required. If the deal is large enough to justify the costs or if enough customers request support Cisco will attempt to qualify it.
Here is the update to the HCL for Unity 4.0:
http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.ee8e2f8
Keith