Furmark will do the stresstesting, display temps (also graph them), display GPU voltage, and also display fanspeed as an RPM and a percentage.
In short, one app that will do everything you need for measuring.
If you need to actually modify settings - that's when you want to progress to MSI afterburner (I just use Catalyst Control Centre, as I don't mod voltages)
MSI Afterburner does way more than this. It is an essential piece of FREE
software for OC'ing, voltmodding and silent computing (fan management). It totally rocks together with a Logitech G15 keyboard with display. Allows you to see all the info on the display while you game of stresstest. Lovely.