Well, if you can find a Viper 520, you can easily add an internal 2.5" IDE drive in the A500. The Viper also adds KS3.0, 8Mb Fast RAM and a FPU. I'll admit that the Viper 520 is hard to find though.
I don't find the A500 ugly. I think it looks much nicer than the A600.
Who the heck wants to go through the trouble of upgrading and even carrying that HUGE behemoth around. I used to have my A600 inside my Cars Dashboard back in 1994 and Had DSS8+ attached to it with a Mic and to my Sound System to yell at passer buys "GET OUT OF THE WAY!!" try that with an A500 in a car...............also had scratch and DJ samples that I would hit keys while driving...........playing my own music
What an odd thing to do. I wouldn't consider any Amiga portable. It doesn't matter how small the thing is, you still need the monitor, mouse, joysticks, etc. But if I REALLY wanted to, I could easily put an A500 behind my 1958 VW dashboard....right on top of the gas tank. ;-)