Add a WIDE Loft to your existing C&C Cagetopia Large, XL, or Jumbo cage (the wide loft does not fit on Small or Medium Cagetopia cages unless it's offset). Wide Lofts really should be OFFSET by one grid (not shown in the current photos), which adds about 15" to the overall cage length. Unless it is offset, you really cannot reach all the way to the back corner when cleaning or refreshing the cage. In addition, since you cannot quite reach, most guinea pigs will very quickly figure that out and that's where they'll run when you want to catch them.
Please see this article for more info about HOW to offset (there are two different styles) and how offsetting changes the COVER needed.