For an A/B switch, how about this:
Made by Jet City Amps and designed by JHS pedals. An A/ B Switcher with a built in boost. You shouldn't get ground loops as it's buffered. JHS make some great pedals. A friend of mine has a few of their pedals and they sound great.
http://www.jetcityamplification.com/2011/02/16/jhs-boost/
$69.99 here:
http://cgi.ebay.com/Jet-City-JHS-A-B-Switch-Boost-Pedal-/380352991560
OR
For A/B/Y, the Radial Bigshot ABY
Has ground lift and a couple of other cool features, but no LEDs. You should be able to tell which amp is on though by the sound...
$79.99 here:
http://www.sweetwater.com/store/detail/BigShotABY/