E6400 to Q6700 for gaming. Worth the upgrade?

I currently have a Core 2 Duo E6400 in my rig and was considering jumping up to the Q6700 but after looking at prices and the CPU charts I'm not so sure. I have an XPS 700 without the upgraded 720 motherboard so the Q6700 or QX6800 are the highest I can go and have them be compatible. I'm ordering a GTX260 Core 216 and 4gb of Corsair memory soon so if anything I would expect my CPU to be the bottleneck in the system.

Has anyone done a similar upgrade and have you seen big results in actual gameplay or are the two close enough for most games that I can get away with saving money and sticking to the E6400? (I normally game at my monitor's native resolution which is 1920 x 1200).

I would love to build a new i7 system but I can't swing the cash right now so the idea is to get a little extra oomph into this one and hopefully build a new one next year. Unfortunately the XPS 700 is only overclockable through ntune which is horrifically buggy, that's what I get for not building it myself though (bought this one used for less than I could have built it for). If you know of any other way to overclock these than ntune I would be ecstatic to hear about it.

I went from a 3ghz E6300 to a Q6700 @ 3.2ghz and really in gaming theres no difference. I mean if you play something quad intensive like GTA4 yeah, but the games I play I have seen no difference. (Cod4, playing STALKER:CS right now)

Honestly I haven't seen any difference in anything. I went with the Q6700 cause it was the best my board could take also. I picked it up for $174 and figure it will hold me over for a couple more years.