Help picking DAC for Bellari HA540 with Tele ribbed plates

Hey first post. I know there are threads very similar to this one, but I didnt want to jack them, plus theyre like 5 years old. Anyway, over the past couple months I've been reading the forums (tons of great info) and I feel like ive gotten myself pretty well set up. My chain goes Akg K702 600+ hrs bun in > Bellari HA540 with NOS Tele ribbed plates > to Gefen TV stereo DAC (optical in) > onboard optical output > foobar 2000 (all flac or wav). It dosent take a genius to figure out the weak link haha. I got so excited about buying my first set of quality equipment that I neglected thinking about my source hence the el cheapo DAC. Well here's the question, which would cause a more drastic improvement, a soundcard with a high quality optical out or a new DAC. My budget for the soundcard is 250 (I do no pc gaming) while the DAC is 600. Currently for the DAC I was looking at the V-DAC and the DACmagic which seem to be the favorites for the midrange price. As for the soundcard it's a toss up. Thanks in advance for any help

yeah im really enjoying it, and it sounds great with the tele tubes. I just want to push the sound to the next level but theres very little info on them in the forums. However if my search for a better source remains inconclusive im probably just going to buy another pair of headphones probably the AH D7000 which I see you already own. I read in a review that they sound similar to the K702's with more bass, which sounds fantastic but from your experience is that true? Also if you can remember, what DAC were you using for the Bellari when you had it