Well, I've cut in 2 IEC's in (gulp) ARC equipment; an amp and preamp. This is not an easy retrofit. Most of us are not experienced metalworkers. I'd *strongly* recommend practing on a piece of metal that matches the thickness of the unit in question. Mandatory, in fact...
The 'nibbler" mentioned might work on the thinner sheet metal in less expensive units, but on thicker plate metal used in more expensive stuff, it's a drill/Dremel job for shure. Dremels tools have a learning curve, to say the least. Either way, you'll generate a lot of (conductive) metal dust and filings. A post-operation blow out is *mandatory.
Was/is it worth it? On the amp, yeah. But now I have to have made some makeup pieces to cover up the really crappy job I did on the cutout. Otherwise, resale value would be a trade for a six-pack. Preamp? Well, maybe. It's a sensitive area, since attaching a p.c. that costs 50-100% of the retail price of the unit envokes a price-performance debate.
There *is a bit of hype in the p.c. market, at least in the sub-$500 area. IMHO. YMMV.