I have a cluster of 3 Sun x4450's w/ 4 Quad Core CPUs and 64GB of RAM each. These are the latest boxes we bought a around a year ago. I've had ESX on bl35p/bl45p, DL385's, DL585's.
I do think HP's remote board is a little more refined then SUN's but both get the job done fine. Like the HP Blades, you automatically get the remote console, and don't need the additional license to view console and access remote devices.
As fo the management question. Can't help you as we don't use either.
