Hi JCHASE88 and welcome to gtg.
When it comes to choosing Power Supply Units (PSU), generally the more expensive they are the better and heavier the build quality and also they normally run quieter. (I have myself bought at PSU for £20 ($40) and it ran almost silently).
My question would be is why you are looking to upgrade from what you have, as you dont mention that there is a problem with your existing one. You would normally only need a new PSU for one of two reasons:
1. The current model is faulty or dead
2. You were upgrading numerous components in your PC which took the total power usage to over 250W.
If neither of the above apply, then I feel you would be wasting your money.
Based on the computer you have (and I admit I only had a quick glance at its specification) you don’t need to look for one that has SATA power connectors, therefore one that only has molex connectors should be sufficient for your current needs.
If you are planning on taking up computer building/repair as a hobby, then getting one with SATA connectors would be an advantage, as most computers now run SATA hard drives. (It makes the inside of the case look tidier and saves the usage of power connector adapters).
In terms of size, most are standard; however measure the size of your current PSU. When you decide to buy one most websites will tell you the dimensions of the one you have chosen.
I myself run an ANTEC power supply in my PC and I can honestly say I have never had any trouble with it.
I hope this helps.....