@ Kasz216
According to a Nielsen study 45.7 million households had consoles in them in the last quarter of 2006 (serving about 93.8 million people). They included any type of console connected to a TV set, so that could be a Coleco Vision, Sega Dreamcast, Wii, PS1, PS3, Snes, etc.
PS2 hardware shipment for the whole of Norh America by 2006: 46.53 million
Let's say about 35-40 million of these were connected to a TV set in the US (playing pirates or original games, second hand, repaired, brand new, etc) in households. That does seem to suggest a high percentage of dual console setups amongst households which have consoles other than the PS2.
Assuming this study and figures are roughly representative, ~40 million PS2s + ~27 million XBs/GCs (relative a very strong market for the XBox compared to worldwide) = ~67 million (~144%), so this seems to suggest it could well be a good majority of US households which had a PS2 next to a XBox and/or GameCube. (Note the US console penetration figure could be a lot lower if Nielsen would have excluded older gaming systems like the NES, Snes, PS1, DC, etc, IMO it would have been interesting if they would have broke up their figures by used platform as well)