Durable/Reliable Laptop With Performance for $400-500

I've poured over your forums for days now and have enjoyed the expertise of this community. I don't buy computers a lot these days as things change so often. I mostly use Linux for my daily activities and I am looking for a dual core/quad core laptop with decent ram/hd and lots of accessories like esata port and slots for sd cards and such.

I'm looking to upgrade this baby over time for the long haul.

Thanks for all the help.

So far here are my picks after going through the forums:

lenovo IdeaPad Z575 (12992PU) Notebook AMD A-Series A6-3420M(1.5GHz) 15.6" 6GB Memory DDR3 1333 500GB HDD 5400rpm DVD±R/RW AMD Radeon HD 6650M

Lenovo IdeaPad Z575 1299-2AU Notebook PC - AMD Quad-Core A8-3500M 1.5GHz, 4GB DDR3, 750GB HDD, DVDRW, 15.6" Display, Windows 7 Home Premium 64-bit, Gray