What monitor are you thinking about getting? One of my next 2 upgrades is going to be the Dell U2410 IPS flat panel to replace my current 23" Acer monitor.
You have to be careful with quad cores. A 2.5GHz quad may run slower than a 3.0GHz duo core if the program you are running does not make full use of the quad. I have a Q6600 and I am actually very disappointed about its performance.
Yeah, with the earlier quad cores, I usually recommended for gamers and such to stick with dual cores as they often had more cache, faster front side bus speeds and faster clock cycles.