The moral of the story is: Don't settle for getting less for more if buying a new system, and expecting any dos or legacy support at all. Broadwell seems to be the last "good" modern CPU which is usable in DOS, bare metal. The Intel (IHD) onboard sound and the Intel VGA BIOS all work well, and exceedingly fast. Modern DOS programs like Mplayer and Mpxplay recognize the IHD sound, which yields exceptional sound in DOS. Linear Framebuffer can enable write-combining caching of VESA 32-bit modes. Also, VGA writecombining can be enabled, for super-fast VGA graphics. Several games also work with DOS audio (PCI "modern" drivers, such as IHD, HDA, and AC97 drivers). At least 7 or 8 games added this support by user patches and / or custom compiles.
My point about speed above is true; a "modern" i7 Broadwell, Kaby lake, or Coffee lake chip supports several times the memory bandwidth that a P4 supports. In fringe cases like archivers, this yields much more speed. There are now FAT32 ramdrives available which will use 32 GB and beyond for a RAMDRIVE. NTFS drivers exist. SSD drive will work in DOS, and can be made bootable via MBR as long as the partition is kept to 2TB or under. R. Loew's drivers enable to use beyond the 28-bit 137GB limit. Every "modern" laptop up to Coffee Lake has provided at least trackpad usability through CuteMouse DOS drive, in PS/2 compatibility mode. Obviously no "real" serial ports exist anymore on modern systems.
However, for general use, I agree, buy a $5 E8500 Core2Duo chip, or similar (overclock to 3.8 to 4.2 Ghz), a cheap Radeon 9250 card, a cheap ESS PCI AudioPCI soundcard, if you can find it. And this will suffice for 99% of the speed and DOS compatibility you need. However, it's still a bit of work getting this cheap DOS system set up, when a relatively modern laptop you have sitting around will probably run DOS reasonably well from a simple USB stick for "free" (no additional system or expense involved!) on bare metal, at very, very fast speed. Just be sure to keep it to Coffee Lake / Haswell (7th / 8th gen intel core i3 / i5 / i7), preferably to Broadwell (5th gen) or lower. That way, you can still have a usable Windows 10 system as well as run DOS bare metal if you want.