Quad-core i7 (or quad core Xeon) is probably the sweet spot comparing price versus speed (along with a well designed motherboard, they are not all created equal). I'm typing this on my primary machine, quad core Xeon and 32gb RAM with Win 10 Pro.
In my experience (and I run a computer business), with Windows 10; 4gb RAM is pathetic, 8gb is sufficient for routine use; the difference between 4 and 8 is HUGE. 8 versus 16 difference is not as much, but still significant. 16 versus 32, the difference is not really all that much, with an exception: If one is running an app where (for instance) it is possible to have all of the samples in RAM as opposed to HD or SSD, then the RAM should be enough to load all the samples into RAM. I have EWQL's Pianos Gold, and it operates in that manner. I don't have any experience with 64gb or higher RAM. Depending on the particular type of RAM needed, it can be one of the most economical ways of getting added performance.
Beyond that, another item that will make a very significant difference is the drive. Even with SSD, there are choices like the NVMe that operate considerably faster than a plain SATA SSD. I have SATA SSD in every computer, PC or Mac, with the exception of two Windows 8.1 computers running Windows Media Center, that are used exclusively for recording and watching HDTV programs. Those machines run 24x7 except when reboot is needed for updates, and standard disk drives are adequate for the streaming in and out of the drive. I make monthly image backups, so if a drive dies, it can easily be replaced.
Another way of increasing performance for lower money is getting something that is discounted because it isn't the latest generation. There is not very much difference in the performance of (example) the hottest quad i7 from a couple of years ago versus the newest; but one can buy the older one significantly lower price. This is particularly important if the choice for financial reasons is the latest i5 versus the older i7 for the same $$.