Josh,
The main benefit is to get rid of the stock power cable. The thin wire, parallel run does hold back the potential of the receiver. The IECs I use, Furutech Gold or Rhodium plated or ACME Silver Plated, all are rated for higher current flow than the figure 8 connector. The DVD type connector is made from tin plated steel. The IECs are all plated over brass or bronze. Both of which sound better than the tin plated steel.
I do not ground the chassis to the IEC. None of the receivers (JVC or Panny) are designed with that in mind. The ground connections are floating and I do not believe it is a good idea to tie them togehter.