Caporegime
I also switched from a q9550 (3.8ghz) to an i7 system, (stock at the minute) primary use is gaming, i wanted to have the option of sli/xfire which x58 offers, also being a newer platform i fancied giving it a try out.I personally went from the Q9550 3.4ghz - 17 920 -3.7 - 4ghz. I have noticed good gains in some areas i use my system for. Everyday use and basic stuff hardly anything except quicker loading etc.
Its not a massive upgrade path for the cost , however it puts you on the latest platform with the more up to date tech.
McT