This is a great EMU site: http://emulationrealm.net/windows.php
I use MAME Plus!, EMU7800, FCE Ultra, Project 64/1964, SNES9X/ZSNES, and VisualBoyAdvanced. I have every rom in every lanuguage for Atari 2400, NES, SNES, N64, MAME /w CHDs, GBA, GBC, and GBX. I use LusSpace as a single front-end that has game-box-art, screen shots, descriptions, and manuals of each game and will automatically un-7zip the rom and launch it with one of the above emulators all on a double click. All of this takes up about 80GBs.
LusSpace is not a good full-screen browser, but it is the best one I have found that supports un-7zip-ing the ROMs and launching them in one click (and then deleting the ROMs [but not the save files] once you close the game). If I wasn't using Good-Merged 7zip ROMs, it would take about 300+ GB instead of only 80GB. I'm sure with some SKINbedding you could get LusSpace to look decent on the CarPC.