As of about a week ago I could have written your post. After several years of digital, I decided to give analog a try with the LP's gathering dust in my basement. Couldn't believe that my system could sound so much more musical and alive.
Michael Lavorgna at Audiostream gave a fairly good review to the SOtM tx-USBexp PCIe card and associated battery supply. Someone on Audiogon just happened to be selling the card with a Welborne power supply and thought I would give it a chance.
Assuming your PC is a desktop, uses Windows 7 and higher, and has a spare PCIe slot, just connect your USB cable to its USB port after installing the drivers. Somehow it cleans up the USB signal, resulting in a better downstream signal. The complete SOtM solution is $750, not cheap.
Chris Connaker at Computer Audiophile has articles on building or buying a PC optimized for music playback called a "CAPS" machine. Three of the four designs are built around the SOtM card. I'm also finding references on Audiogon and other web sites where people claim that less expensive cards give equal or better results.
The bad news is that a clean LP will still sound better. The good news is that you should notice more detail, separation, and greater musicality with your digital files. You may actually wish to raise the volume. I have tried it on my Eximus DP1 with Audiophilleo and currently on the Schiit Loki DSD DAC. Both sound very good.