Help replacing my x61t

[renny]

I've finally admitted that it is time to upgrade from my trusty x61t that I've had for many years. I'm considering getting a used/refurbished t420 or something similar to replace it. I'd like something a little quicker and with a slightly bigger screen than the x61t. I never really used the touchscreen. It will be used mostly for programming, web development, and general browsing. I'll probably upgrade to an SSD and 8 or 16 GB ram. Heat and fan noise are important. I'd like to stay under $400. What would you recommend?