To repeat what Adam said, welcome to AH.
Can you say what makes you think the sound quality you now have is not good? Do you hear something specific that you can describe?
The reason I ask, is that changing speakers often leads to a much greater change in sound quality than from changing receivers. It should be easy to find a new receiver that will meet your needs, but it may not sound much different from what you now have.
Most DACs built into AV receivers are not at all bad. However, it is fashionable, especially among audio magazines and equipment reviewers, to push people into thinking the existing DACs in their receivers are inadequate.
Over time, I've heard 5 different DACs at work. Two were built into different receivers, and three were built into different CD, DVD, or Blu Ray players. I can confidently say I didn't hear a large difference among them. If there was only a slightly noticeable difference, I may not have heard it because I didn't make direct listening comparisons. But it has been my (somewhat limited) experience that different DACs make, at best, only a small difference in sound quality.