I my last car (Renault Laguna) it had a spare din and was a company car that I only had 1 year left on it, so I went for the 2 HU option.

My new car (another Laguna) should arrive in 4 weeks. Now however it doesn't have a spare din slot (they filled it with Sat Nav), so although it's also a company car I'm going to replace the HU with the empeg and also get an amp. Mainly cos I can then use the stalk controls, which will save me messing about with the remote or pressing buttons. Might also try hooking the display upto the nice colour lcd screen that the satnav uses as the factory cd/tuner displays stuff on that.