well, i bought my laptop off ebay, and it turned out fine. you may find it tricky to get a laptop with absolutely everything you want, but consider doing the memory upgrade yourself, it's remarkably simple on most laptops - you unscrew or unclip a panel on the back and simply clip in the new memory chip in the same fashion as the existing one.
to work out what memory you need for a particular laptop, go to
http://www.crucial.com/uk
when buying laptops off ebay, try to stick to the dealers that sell tens of laptops everyday. they are usually refurbishing agents for specific laptop companies like dell or ibm.