Dazed and confused about streamer upgrade

I started a thread in the amp/preamp section asking about an integrated amp upgrade and got some good advice that made re-think my upgrade path.  I have a Macintosh MA8900, driving Vandersteen Treo CT’s, with a six pack of Rel S510’s.  I use a BluOS Node 2i as a streamer.  No CD’s, no need for storage.  I had thought about upgrading the Mac to a Boulder 866, but am now thinking I may get a bigger improvement for less dollars by upgrading the BluOS next.  I don’t know much about DACs and streamers, but am thinking that I should look at streamers only, since the 866 has a good DAC, and why pay for a combo DAC/ Streamer when the DAC will be bypassed.   Suggestions for a $3k to $5k streamer?  Or stick with upgrading the Mac? Thanks for any help!