Displays and keyboards are very personal items. Unless you get up close and see one in person, you don't want to buy any laptop sight unseen.

As to the CPU, that's not the only criteria when picking a laptop for performance. Even the first gen i5 was very nice compared to the usual C2D models. What are you using now?

As to RAM, it's so cheap we bump the machines to 8GB all the time. And from 4 to 8 GB, for most folk they can barely tell we did that. But at the office the payback is worth it. Figure it out. 40 bucks of RAM is how much time? If you save 5 minutes a day then the payback is in a few weeks. Any CFO will invest in that one.
Bob