amp to buy?

Diminishing returns set in much faster with a DAC than a power amp. Some speakers are very difficult loads, and need an amp capable of a lot of wattage even down to low impedances, whereas what speakers you have is of no importance to the DAC used.  
 
An integrated unit is much easier for those just starting out.  
  
A DAC typically doesn’t go straight into an amp, unless you have a way to do digital volume control, but even then there may be a glitch and the signal may be reset to full volume, and you could do some damage. 

In almost every case, the DAC is going to plug into the wall...and then send its signal to a preamplifier and in some cases direct to the amplifier. 


Some amplifiers have one input and a volume control and therefore can usually be fed directly by a DAC whether it has a volume control or not. (One thing to note....if the DAC does not have a volume control with a remote, then you will be stuck adjusting the volume manually on the DAC).


Here is an example of a really good amplifier with a volume control....designed to be fed by a DAC...and can almost certainly be had during their summer sale for at least 20% off.

https://www.cherryamp.com/the-stm-store

https://www.audiocircle.com/index.php?PHPSESSID=dutekkr2qvornd8kdcdpbdiq94&topic=149310.0

Other amplifiers, that do not have a volume control can also usually be fed by a DAC...but then the DAC must have a volume control and the volume control must be set so that after shutting off, it stays at zero and does not reset to 100%.

It is also worth noting that some people will tell you that using a preamplifier will give you a "better/fuller/more realistic" result.  Others will tell you that if the amplifier was designed so that it might be fed by a DAC...then a preamplifier is not needed.

IMO, two "foundations" of a system are the amp and speakers, pick one and build from there. You may find an "all in one" box like Naim Uniti and others is best for you. Going separates requires some knowledge of system matching unless you have a brick and mortar dealer you can trust.

Are you building a system from scratch? What is your budget? 

We live in a wonderful time where it is possible to stream tens of thousands of CDs for about $20 a month, for lossless streaming. 

I stream Tidal and Qobuz integrated under Roon running on a Mac Mini. You’ll need something to stream to the DAC. Do you have a computer you can use?

 is it more important to have a high quality amp or DAC?

As DAC technology is improving almost by the day, I would opt for a high quality amp and get a 'very good' DAC, preferably one that can be upgraded.
I use Ayre Codex, but Schiit makes a Gungnir and Yggy that compare favorably. Both companies offer upgrades when available.
If you are starting out, it makes sense to listen to as many speakers first.
When you find the sound you like, you can then pursue compatible amps and preamps and DAC's.
Where are you located?
Bob