House Battery Replacement - Duracell GC2-AGM: We have a 2012 Allegro Bus 43QGP which was built with six Interstate 6-volt GC2-HD-UT house batteries. Have any of you Tiffin owners replaced your house batteries using the Duracell AGM 6-Volt GC2 battery that is available at Sam's Club for about $180 each? This seems to be a good price for an AGM (no adding water) type battery.  Just wondering if anyone has had first hand experience with these (Duracell AGM 6-Volt GC2) as house battery rep