T400 CPU Upgrade Path

[someuser_nm19]

I just got a T400 and I'm loving it. It came with a P8400 and I recently upgraded it to a T9400. It was like night and day. But I want to get as many years out of it as I can, so I was wondering if the T400 can handle a Core 2 Extreme QX9300. The TDP is only 10 more watts, I was wondering if any of you guys could weigh in on if it could handle it. The model I got has the ATI graphics so it has more a beefy cooling solution.
-Thanks for your time and any help

[RealBlackStuff]

But I want to get as many years out of it as I can...

In that case stay away from any extra room heater, i.e. no Quad core CPU!

[Droider]

T9900 or X9100 is the furthest you can go with. I would put a T9600 myself considering the price/performance and possible heat issues.

[theterminator93]

With undervolting, CPU clock and fan speed management you should be able to keep the heat down sufficiently to let it run well enough with whichever CPU you use, assuming no prolonged torture sessions! You'll need to decide if you need higher single-threaded performance, or a slight boost in overall performance with multi-threaded applications (and more heat).

The T9900 in my T601f runs pretty cool overall; I have it undervolted a bit which helps immensely. At 100% utilization on both cores it will get into the mid 70s with fan on high - so I'd imagine with twice the cores (at a lower clock speed) you'd get pretty hot.