Recommend R5x to use with ThinkPad Dock II?

[Edward Mendelson]

Time to replace the old ThinkPad 600X/SelectaDock III combination in the office with an R5x model (which I don't yet have) and a shiny new Dock II which I just got on eBay. Question:

Can anyone recommend an R5x model that will work in this setup and still (I hope) be useful for a number of years in the future? The machine will spend much of its time in the dock, driving an external monitor, and will stay in a locked filing cabinet at night. Speedy performance matters more than whizbang graphics (which aren't on the R series anyway, it seems).

Many thanks for any suggestions. The current special-offers on Lenovo's site seem to be R50e models, which I think don't work at all in the Dock II, so that route doesn't seem feasible.