Dell tends to load their systems with tons of extra crap that severely impact game performance. XPS systems are good after you spend several hours removing said junkware and don't mind paying extra (Dells are a bit overpriced too).
I'm not sure how good Cyberpower is for their laptops. PC Magazine seems to like them pretty well, but they also like eMachines.
cyberpower is great for laptops but make sure you get what you buy! My brother got one a few months ago and they dropped in a 5400rpm hdd instead of a 7200rpm. They were great with the switch but come on...thats like a $75 slip up. He got suspicous of the writespeeds etc and looked up the specs in the BIOS. it turns out the company that made the hdd he found inside didnt even make a 7200rpm...