im running my pc threw my onkyo 609 great sound for watching movies, but not good for listening to music, i thinking about geting a hifi amp and dac budget about £600.
My money would go on a Onkyo ND-S1, which takes the digital USB from the PC and feeds a digital Coaxial to the Onkyo. They are £120 new. Best bargain buy I ever made. I use it for streaming Rara and Spotify, as well as FLAC. One is connected to a Naim Supernait and the other a Naim Uniti.
Do you need USB or optical digital connection? Or both?
If you only need USB then the HRT Music Streamer II is £159. (It's async USB and will handle up to 24bit/96kHz unlike a lot of USB DACs)
That leaves £441 for an amp. Can you stretch it to £498 for a Rega Brio-R?
The Cambridge Audio 651A amplifier (£449 Richer Sounds) has a built in USB DAC but it's only 16bit/48kHz. (You could add the Cambridge Audio DacMagic 100 for £200.)