As regards RAM, no matter what computer you buy the cheapest RAM will be the upgrade you buy yourself on NewEgg or similar. RAM is literally the easiest thing to upgrade, the PC supplier always overcharges for it, and there is no reason not to just buy it separately.
I'd go for an intel i5 processor if I were you. The unconfigured ThinkPad I linked looks nice, although with any computer the first thing I would think about is how worthwhile a RAM upgrade (do-it-yourself edition) is. You
want 8GB, trust me.
Intel and AMD are both decent, though most would say Intel is better (arguably AMD exists because Intel put up with the competition purely to stave off the antitrust hounds).