Having been a customised computer builder with prc-data.dk for many years,
I would advise, that you know exactly what you want.
Desk top publishing, high graphic work, gameing, multi-media multi-level tasking, there is much to look into, and it's just a waste of money, if you don't get it right.
Compatability testing is very difficult and almost not possible for retail outlets, due to the specialised run in and monitoring of components, over at least 24 hrs, to pick up any system hangs, specialised bench marking applications are used.
Although what you can do, is search out the best machines on bench marking websites, check out the forums and reviews, to discover what is the Royals Royce of today.
There is a saying in the computer world, "That you don't need a Lamborghini for doing the job of a mini" otherwise, your money is just thrown out of the window.
Retail shops and many computer builders, will be happy to part your money from your wallet.
So do your research on the internet and discover what specification suits you, check the bench marking reviews, and list the components and hey presto, all you need is someone to put it together, that knows what they are doing, to tweak it, for best performance.
You may find what you want at
they used to do benchmarking, years ago, early 90's not sure if they still do, although there are plenty of other websites around, to search out your dream machine!
Once you find it and it is tested on the bench, check for reviews of the specification, list them, and build.
The main problem is many people want the best and fastest, and when you ask, them what they wanting it for, they say Desk top publishing! So you get the "Lamborghini, when you really only need a mini"
What will it be most used for? Go for it