Hi, knightguy82.
Unfortunately, upgrading your desktop will take a little more than a simple motherboard swap. But, you should still be able to upgrade your desktop to a better setup than a laptop for a lower price.
If I may make some recommendations on parts, here's what I would look at for upgrades:
- CPU: 5th generation Core i5 or Core i7 processor: with the 6th generation processors out, the 5th generation CPUs are falling in price. The Core i5 4690K, for example, is a pretty powerful CPU.
- Motherboard: Socket LGA 1150 motherboard - good brands include ASUS, Gigabyte, MSI and Intel. The MSI Z97-G45 motherboard has great expansion options (it's very similar to the motherboard in my current system).
- Memory: Minimum of 8 GB memory. Most modern motherboards will take between 16 GB and 32 GB. This Kingston 8 GB kit should work very nicely, and the 16 GB kit isn't much more.
- 64-bit Windows: Once you have more than 4 GB memory, you need the 64-bit version of Windows. Windows 10 Home 64-bit on a USB flash drive is a convenient choice.
- Graphics card: Okay, so you don't need a new graphics card for The Sims 3 - your current 550 Ti will play it just fine. However, should you want to play other graphics intense games outside of TS3 or TS4, the GTX 750 Ti is an excellent choice for inexpensive gaming.
The type of case you have now will determine what size of motherboard to buy. I'm assuming ATX, so you may need to search for a similar motherboard if you have a mini-tower, for example. One other note is if you plan on running two graphics cards in SLI (nVidia) or Crossfire (AMD) mode, you will want to look at a different graphics card as the GTX 750 Ti does not support SLI.
Hope this helps and happy Simming!
Flynn