X2 (recently purchased by Line 6) makes a rackmounted wireless system, the XDR-95. This system doesn't use a compander (compress and then expand the signal on the transmitter and receiver ends respectively), but instead uses 28 bit A/D conversion and has a 10 Hz -20k Hz frequency response. JICYDK, for reference, the low E string sits at 41.2 Hz.
$499.99 pretty much everywhere, but music123.com has a sale on now where if you spend $500 you get $100 off; buy some picks to put you over the target; did just that a few days ago and can't wait to use it. This is, supposedly the system if you want to go wireless but refuse to alter/sacrifice your bass tone to do so.
Complete specs, reviews, etc. on their website.
http://www.x2digitalwireless.com/pro...instrument.htm