Here's what I'll say regarding dacs and amps.
Do you really need a dac and amp? Well, if your motherboard audio picks up electrical noises causing you to hear whiny sounds in your audio, or if you need special features like dsd, etc (I don't think motherboard audios can do that? Maybe they can, but I don't have dsd files so I don't know).
Do I need an amp? If your audio is fine, doesn't have electrical sounds being picked up, however, you feel that the audio is kinda quiet even on 100% or you have high impedence headphones that require more power, then yes, an amp would help you.
I personally got a dac and amp because I felt that my motherboard solution was emphasizing the bass a bit too much (cause gaming audio solutions and all that) and for some reason, gpu coil whine would make its way into the audio output.
Regarding combo, I asked a similar question regarding the o2 and sdac, and the replies were that the o2 amp is outdated and has been replaced by the jds atom. So I suggest giving that a look. There's a review and based on the measurements, it's amazing for the price. As for dacs, the topping d30 was a suggested option, the sdac will work fine as well. I also suggest the fifine mic. It's simple stand mic for like $25. It's a very cheap and good solution if you need a mic for vc. Do note that since it is a stand microphone, you'll have it near your desk, so it might pick up keyboard noises depending on where you place it. You could get a stand for it... I think they are compatible but not too sure.