Any high end video card is likely going to need more PSU wattage than what is already in this case. Does your PSU specify the wattage so you will know if its just a 280watt supply or a 400watt supply etc? Also looking at pictures online, I havent found any internal pictures of this minitower, but you may be able to install a full-height video card into it unless they have some sort of riser card setup that forces you to a low profile card. Simple measuring can verify if the card will fit before buying and installing. You can do this by cutting a piece of cardboard to the same dimensions of that of the card you want to buy and install and then open the computer and place the piece of cardboard in where the videocard would go ( without stuffing it into the PCIe slot
). This will point out quickly if anything would conflict with the video card installation such as ( components on the motherboard such as tall capacitors, chokes (inductors), heatsinks, connectors, cables such as SATA ports, CMOS battery connector upright vs flush with board, may conflict with the installation of the card you want to install.
Basically if the cardboard test passes with no issues, it should install with no surprises. The only catch then is if your Power Supply can hold up to the increased wattage load of a heavy duty video card. And if its not high enough wattage to run it without overheating it would have to be replaced.
But... your options for getting this converted into a serious gaming rig is not over yet if you have conflicts of video card fitting or a larger power supply not fitting. There is a cheap solution, which is to buy an inexpensive computer case ( some come with 500 watt power supplies ), which can be populated with your motherboard, and drives, new PSU and video card, and you now have a self built gaming rig for all of your gaming desires. This is the easiest solution if you have clearance issues. *If your system has a riser card though as mentioned earlier, you will want to make sure that its a normal motherboard with the riser attachment, so that the riser can be removed and thrown away and this motherboard can run without it in the new computer tower.
Another advantage of using a new case is that the Packard Bell designed case might not have adequate airflow to handle the increased heat created by a high end video card, so you might find that you have to run the system with the side panel off or it turns into a toaster oven inside.
I had issues a long long time ago with a Packard Bell running a (crippled by design) Cyrix 133Mhz CPU ( one of the worst CPU's I have ever experienced the pain of supporting ) which the customers computer was to be a gaming rig for their teenager (around Christmas 1997), and the parent asked if I could convert/upgrade this low cost computer that they got a great deal on from Circuit City into a gaming rig for Quake II etc and I had to plainly state that this computer will never be a gaming rig with that motherboard with that CPU. And its way too proprietary to try to fit a universal AT motherboard into. I suggested that they return it for a refund and buy a system with an Intel Pentium II 233 Mhz CPU, which would be able to run Quake II as well as other high end games out of the box without any upgrades, since its likely paired up with a decent video card or integrated GPU with plenty of RAM. With bare minimum being a Pentium 166Mhz even though Quake II can run on a Pentium 90. They bought it on clearance and were not able to return it. They asked if I knew of anyone who would buy it at 75% the cost they bought it at, and I stated that I wouldnt want my reputation tarnished by selling that inadequate computer to anyone. I suggested they list it in the newspaper for sale and try to get someone to bite at it for 75% their cost OBO. I think they unloaded it for a $400 loss to someone who didnt game.
The good thing is that your CPU is a good one for games, so your not in the same situation BY FAR !!! Your Core 2 Quad 2.5Ghz CPU scores a good score of 3066 at
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core2+Quad+Q8300+%40+2.50GHz and CPUs that score just 1500 -> 2000 would likely run the games you want to run paired up with a better video card.
