you can probably buy an i3 with the same amount(not sure, not updated with pricing) , but with a not-so-good mobo.
but with the ROG and 9550, you can hit high clocks, just OC it. and i have to admit, the ROG appeal is hard to resist, esp if you cannot buy the latest ones and if it's ok for you to have an older tech pc
an I3-3220 is faster than a Q6600 at 4.05ghz with the same GPU (560ti) so it depends if you have 100$ more for a new rig or not...
PS: my Q6600 SLACR G0 needed 1.6V vcore to get over 4ghz (the max is 1.5V in the Intel specs) so i doubt you'll get close to 4ghz without really want it and as this is an used rig, stability is always a challenge (all parts have some degradation over new parts)
@Valentin Yes, i'm planning to upgrade it in 8gb if i take this will. so its wise if i just get this deal and try to O'C it? or should i just get newer tech just adding some $ and wait for a month
If the energy-bill is not an concern then try to overclock it but I personally would go with the new tech. You can also wait for haswell to come out on 15th of Jun or July; We are in April, next month is May where you would do the upgrade and Jun is next ahead.
With two months saving you might more and get a decent quadcore.
You can also change the direction from Intel and go with an AMD FX cpu, it's all up to you. However I don't know when steamroller cpu will come out (it's said August).