DAC: high quality USB + preamp $5000

I gonna purchase a new setup for my large room in the nearest future. I'd like listening to music by the computer mostly PC and Foobar2000, but it's usually disgusting sounding via USB from a lot of DACs, more worse than their AES inputs with external CD-transport or internal CD-drive of classical Players, unfortunatelly.
Also, a full preamplifier is too expensive for me.
So, What DAC up to $5-6000 could be prefered for connection to PC via USB sounding not worse than AES input and with high quality internal preamp not worse than separate preamplifier?
Thanks in advance for any advices!
(Sorry for my English)