[ammitz, you replied as I was typing this

]
Definitely don't use a jigsaw to cut the finished profile.
What I would do is make a template from a scrap piece of material and then use that to template route the hole.
Route a circle to the required size in a scrap piece of MDF etc. To do this you can simply make/use a tramel like this:

You will however be doing it to create a internal ring template, not a circle like in the picture above.
Once you have a template you are happy with you can line this up on your cab side and mark the profile. Remove the template and use a jigsaw to remove the bulk of the material. You will need to drill pilot holes for the jigsaw blade to start in, be careful when drilling these so that you don't get breakout on the other side. You may need to have some scrap material on the other side to prevent/minimise this.
Once you have removed the excess you can fix the template to the cabinet profile with double sided tape, or ideally clamps if you make the template big enough. You can then use a pattern or flush trim bit (depending on which side of the cabinet that the template is) and trim the excess off.
Using this method you should be left with a nice, clean hole. I would advise practising the whole procedure on some scrap material first seeing as you are doing this to a finished cab.