Re: whos pc is better...
Your comp should be better for gaming. I have a P4 3.06ghz processor and can do practically anything, however heat is the biggest problem with it. Temps can get very high, very fast without the adequate measures in place. Your 7300 should do nicely compared to an x300se. Lol, I have a 9250 and halo was a bit choppy on my comp too. I turned down the decals, and shadows, and kept it at 30fps. The Vsync feature made it feel robotlike, lol, dont ask. Now it runs great without any lagging. The online games never lag unless the host has too many people on their server, or if your connection is too slow, so its not really your video card for when you game online. Try getting faster internet if that is your major concern.
Rig -- Emachines T5026, 3.06ghz P4, 300W Bestec PSU, 160 sata hd, 512mb dual channel 3200 ram @ 3-3-5-8, ATI Radeon 9250 pci, dual layer 16x dvd+/-rw.