An important decision needs to be - your expectation and than how much you are willing to spend. Beyond that would be if you want a pre-built or a custom? In order to address these points, you would need to do some research. As a ball park figure, I'd say a very basic adequate PC for use with Hauptwerk presently can be built
starting at $1,000 USD.
I made the PC vs Mac comments because with a PC there are many more decisions to be made. Very recently, I was asked to help a Mac user wanting to switch to a PC. I went thru an abbreviated list of PC questions, even referring him to PC Part Picker and several other info sources. The present situation - his comment 'I never had to do all that with a Mac. I think I'll stay with the Mac.'
Consider a simple question such as what case do you want? I can easily think of at least 60 possibilities. Then the electronics with each one have likewise many. And each decision in many cases affects many other decisions. Not at all trying to dissuade you from going with a PC, Meself, I have.presently 4 different flavors of Mac's here from a Mac Pro to a Mac Mini. And many species of PC's as well. No such thing as one size fits all. There are many Forum members who will share with many saying given the choice they might do things differently. .A point of consequence is the present lack of components/chips worldwide which will probably last for the rest of the year. I'm looking for some specific parts which cab had, but at ridiculously high prices. I check Amazon and Newegg dailly and their prices keep increasing. So do you want an average,adequate PC or have specific requirements such and how many and which sample sets. What about your audio requirements?
Slightly off the, but my wife and I used to frequent (often) a restaurant in Chicago -
Soup's On. What was so neat was the menu -4 different, all you could eat, homemade soup. (Which changed daily). Trying to get the right PC (for your needs) isn't simple like that analogy.
As a starting point, why don't you spell out what you have presently and what you may want to add to that.
You can expect any reputable custom builder will ask many questions. I'd think a bit if a builder has 'just what you need' because he may be.trying to move some outdated parts. My present PC that I built very recently is using a 7th generation CPU while presently a popular CPU is 10th gen. This discussion about sockets refers to the CPU socket on the motherboard which vary according to the CPU.
Keep in mind, the right PC for me may not be the right one for you. Above all, don't be intimidated by all this tech speak.There isn't one here who was "born" with all this knowledge. The best is to attempt to make informed decisions and this. Forum has some of the most knowledgeable anywhere. Any many of these most knowledgeables don't comment unless they feel they have something to contribute at their level.
You might want to spend a few minutes and watch this video as it may help to answer some of your questions. Even if you've never considered building your own PC, it is very doable. and you'll come away with
knowledge.
https://www.youtube.com/watch?v=_71ArmcP9G8Rgds,
Ed