Arrafiq, Your situation is a tough one, which is why I think you didn't get any responses initially.
I would make a couple of comments here about how I generally approach situations like yours. We have all started someplace, and dealt with budgetary limitations. You got a taste of what good equipment can do for you with your LSAs, and I would add that I think you made a wise purchase there. Those are speakers that you are going to be able to hold on to for a while, and as you put better equipment in the chain, they will continue to deliver for you. That is the correct model going forward. Sometimes, that means you delay purchase until you have enough available to get that next component that will push you to the next level. That can be frustrating, but it will avoid a lot of wasted money spent on making marginal improvements. Thinking about your situation, something like a ModWright integrated with built in DAC would be perfect, but it is way out of your price range, even used. I took a look for a used integrated for sale that would work for you and didn't see anything for sale right now.
The modwright stuff is superb in my opinion. Every once in a while one of the Modwright integrateds come up used, but I haven't seen any used ones with the built in DAC hit the market yet. This would be an option that would without question be worth waiting a while to procure.
I take it you are using the apple TV as your video source, so that you currently have no playback capability for DVDs or CDs, and it is your desire to continue with that set up going forward. Sorry if I am being dense, but I'm having a hard time wrapping my head around that. :)
Thinking about this more thoroughly, if I have all this right, I still thing the oppo 105 may be your best move if you are locked into $1200 at this time. You can still use your apple tv for video if you want, but you can use the much better DAC in the oppo to real advantage with music, it has wifi capability, and it also brings physical media capability into your system.
A DAC with USB capability may still make sense, but you have to provide for connection to your digital files, which may or may not be practical. It seems to me that the Oppo circumvents all of that and you get a good dac along with all the rest it gives you.