Jen on pea et 40.       Showbiz Spy: Hugh Hefner says he is "much impressed" by Jennifer Aniston's nearly naked  January GQ cover.    The Playboy baron has Carmen Electra gracing the cover of his magazine's 55th anniversary issue.    But, after seeing former Friends star Aniston on the cover of GQ, Hefner says he wouldn't be averse to putting the 39-year-old Jennifer on the cover of his publication.    He says, "This looks like the cover of Playboy. I'm much impressed by Jennifer.    "Is it just me, or is Jennifer Aniston getting hotter?    "Never seen her in this  light before."