I completely understand the desire you make your money last as long as possible. I think you have already picked out an excellent price point that has the best value for the money. When I make a purchase I usually aim to purchase a top-of-line unit because some how it assuages my concerns about its durability and usefulness. But what may have been sound economics many years ago, no longer apply to electronics. I think the best option is to purchase something that fits your needs now and for any software you think you will be running in the foreseeable future; not necessarily software that you think may come out in the future, but software you don't have but think you might buy. Productivity software and web browsers will certainly run on any machine you purchase today. Newer version will continue to run on the machine five years down the line. But games with latest eyecandy features likely won't run well on older hardware. This is specially true of notebooks that have slower equivalents to their desktop counterpart.
Just in case your interested in the switchable graphics feature...
All new notebooks that have the feature list it under the marketing terms Optimus (for nVIDIA) and Switchable Graphics (for ATI/AMD). Many notebooks can be hacked to enable the feature, but your mileage and desire to mod your notebook may vary.
nVIDIA has a list here:
http://www.nvidia.com/object/optimus_technology.htmlAFAIK ATI/AMD does not have a list, but there is a list compile of both ATI and nVIDIA notebooks compiled by netizens:
http://forum.notebookreview.com/wha...49-list-laptops-switchable-graphics.html