All I know about Dell switches is not good.
The original dell switch products are cheep switches with that I had only trouble.
Dell aquired Force10 , these parts are a littlebit more professional.
IMHO
I would never replace an ERS8600 with Dell gear. If you donīt wont to use Avaya switches for your replacemnt take a look at Cisco, Juniper or Brocade.
Cheers