Yep, you've got it.
For EVC, you need to look at the CPU architecture that your IBM HS21's have. I think they are Penryn, but I could be mistaken.
On the HP blade cluster, you'll need to set them to use the Penryn (or whatever) EVC mode. Once you have that set, try the lifeboat method on an IBM blade with a single test VM and see if you can live migrate it. If it doesnt work, you'll know you have to try another EVC mode.
I don't have much insight on storage, so I can't really speak to your second question.