You will not drive the HD650's sufficiently with simply a headphone output from a laptop or a desktop. And I would not use any sort of sound blaster card to drive them. No. Simply not good enough. That's why they sound "just ok". They are high impedance headphones that require a decent amp to drive them, and a decent DAC to drive the amp.
First off, what is your budget? You don't want to go cheap with those cans. I guess you could if you must, but honestly, you won't do justice to them with something like the Bravo.
If you are on a budget, the bare minimum I would go with is a Schiit Modi DAC, and the Schiit Vali amp. Yes, you could go with the Bravo (and I'd use a v2), and replace the stock Bravo V2 tube with something better from eBay ... but every report I've read in the Vali thread indicates the Schiit Vali is superior to the Bravo (any version). You'll spend somewhere around $220 bucks, but that's the very least I would do for those cans.
However, if I were going to recommend something really appropriate for the quality of the HD650's, I would go with the Schiit Bifrost Uber, and a Bottlehead Crack amp. If you don't want to put the amp together, then go with a Schitt Valhalla amp instead. Either of those setups will yield results more appropriate for those headphones. You will spend around $800 for that setup, but it's far more appropriate to really put them to good use.
(I am assuming of course, that you're wanting a tube amp of some sort.)
Edited by UmustBKidn - 2/9/14 at 4:15am