|This is a desk PC and logically it doesn't move around.... So a cat-5 connection would be logical here; stable signal, and faster too...|
Homeplug systems are ideal here; both cat-5 and even a wifi module if preferred.
Depending on where you are based UK/Europe or elswhere determines a little which brands to consider. If you're able to use Devolo they would be my top recommendation.
You would two modules at least; one connects to the router, the other to the PC - both via cat-5. And that's it.
Your current poor (no...) signal effect may be due to shared channel interference; in that there are others in your immediate area using the same wifi channel s you? Perhaps change channels on your installation, and see if it helps?
The wifi card involved may not be the best; equally check for firmware updates?
But overall I'd consider the homeplug approach - lanover mains...