Greg,
  I'm in the middle of such an upgrade.  I'm putting one of the Sony amps
  under the pilot's seat -- can't remember the model number offhand (XM1805?),
  but I'm only feeding the dual ten-inch subs 100 watts each and the component
  5" mids / 1" tweeters 40 watts each.  Anyhow, the well under the driver's seat is something like fourteen inches
  wide by five inches deep (deeper near the back, obviously), and really
  really long (that's a technical term right there).

Best,
d.

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