Dual Batteries-Battery Weight

We are going to be installing a dual battery set-up. Should the weight of the extra battery be a concern to us in the front end or is it no big deal? Are you better off running into the cargo department (which I prefer not to, since I use that space).

Also, I was looking on Wrangler NW web site, I noticed instead of an Isolator like I'm use to seeing, they use a Battery Isolation Relay on their dual systems. How does this differ from a regular Isolator?

Considering the weight of the after-market front bumper, front skids, etc. that I have added I would be surprised if it was a problem.

That was my actual concern, with the weight of HD bumper, winch, etc., when does it become a concern of too much weight in the front end?