streaming pre/dac for kef ls50 w

I bought a pair of Kef ls50 wireless for my office ,  I would like to add a preamplifier with streaming capabilities and a good  DAC.  I am very pleased with the quality of Amazon HD , so I wouldn't use any other source . 
Any ideas ?  Budget  less than us$  2000. ( less than  1000 ideal ).
Any suggestions ?