Another vote for the Dells.
Get a Precision model though. They're the ones designed for power users. They are more 'mobile workstations' than just laptops though.
If you really want a good deal, get a factory refurb on eBay. Most of them are 'as new', fully refurbed by the factory, and come with the full warranty. You can of course try and get one off the Dell Outlet store, but I just find it easier to get one off eBay.
The m4600 is the 15", while the m6600 is the 17'. These have the 2xxx Intel processors.
The M4700 and M6700 just got released, with the 3xxx Intel processors. You won't see much difference in performance though between the two. Save some money and get the M4600.