Inspiron 546MT Upgrade

Hello,

I have an Inspiron 546 MT and I would like to upgrade the graphics card and, if needed, power supply. I understand I need to ensure the graphics card is PCIe 2.0x16 compatible but I'm not certain about the limitations on the power supply. Is there a maximum wattage I should be concerned with when determining what power supply to purchase?

I want to be able to play video games, such as Star Wars: The Old Republic, on medium-high to high settings. Any recommendations on which graphics card to buy? I will be purchasing a Corsair power supply to accommodate the graphics card's power requirements.

System Information:

Operating System: Windows Vista™ Home Premium (6.0, Build 6002) Service Pack 2 (6002.vistasp2_gdr.110617-0336)
           Language: English (Regional Setting: English)
System Manufacturer: Dell Inc.
       System Model: Inspiron 546
               BIOS: Default System BIOS
          Processor: AMD Phenom(tm) 9750 Quad-Core Processor (4 CPUs), ~2.4GHz
             Memory: 8190MB RAM

        Card name: ATI Radeon HD 3600 Series     
     Manufacturer: Advanced Micro Devices, Inc.
        Chip type: ATI display adapter (0x9598)
         DAC type: Internal DAC(400MHz)
       Device Key: Enum\PCI\VEN_1002&DEV_9598&SUBSYS_22421028&REV_00
   Display Memory: 3059 MB
 Dedicated Memory: 248 MB
    Shared Memory: 2811 MB
     Current Mode: 1920 x 1080 (32 bit) (60Hz)