If you want a good sturdy machine that will last years, have 3 to 5 year warranty and good tech support/NBD on-site repair then look at the Dell Latitude range which includes an ultrabook.
Not the cheapest but you get what you pay for.
As for memory, always buy the machine with the smallest option and then get an upgrade from Crucial. I recently bought a new Latitude, wanted 8 or 16 GB of memory but went for just 4GB. The cost increase to 8GB was more that 16GB from Crucial! Not just Dell, but most off the shelf are priced in that way.
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