Sandy Bridge i3/i5/i5 upgrade - avoid the one that overheats

Members of this forum have already helped me to make a choice between different DDR3 combinations.
Next in line would be the CPU, which will be the last modification.
The laptop in question is Dell n4050:

- Intel B815
- Intel HD Graphics (G2 Pentium/Celeron 1.1/1.15 GHz) Dell(1028 0502) 786MB
- Sandy Bridge HM67 Motherboard
- Samsung PM851 256GB SSD
- 2x4GB DDR3 1333MHz, Kingston

I have been given an offer to switch the above mentioned feeble processor to a much normal iteration of the Sandy Bridge architecture. The offer, given by a small local shop/repair service, is one of the following CPUs: the i3-2350m for 20$, the i5-2450m for 40$, the i7-2640m for 50$, or even the quad-core i7-2670qm for 50$.

I am planning to use this machine as a secondary computer. Just for regular work, nothing professional nor business related. But, I am still tempted to buy the i7 CPU, just to see hot fast one of the top dual-core 2nd gen processors is. The only thing that worries me is will the i7 CPU overheat while processing basic tasks? Watching 1080p streams? Is it a smart choice? The shop will not charge me if the processor doesn't work inside my computer. Therefore I am not burdened by that. The only thing worrying me now is the emission of heat.

The current Celeron CPU actually heats a lot during hot summer days. But, just for example, when the air is cooler, the software monitoring the CPU temperature never showes more than 72 C. And that is when I intentionally push it to the limit.
Will the dual-core i7 overheat? If I'm not mistaken, it is rated at 35W, therefore should perform similarly?

 

Its unlikely the temperature will be an issue. If anything you will have lower temperatures if you are going to use a higher quality thermal paste than the crap they put on in the factory.

 

@GoodSir Pentium/Celeron generally tend to run cooler, despite same TDP. I'd try i7 2670qm, and return it if it runs too hot.

 

@Starlight5
Could I, for example, use the Win10 option which limits the CPU power and somehow "tame" the, otherwise high (45W) TDP, quad-core? It would still be quad-core.
I truly don't need all the power that CPU has. Sometimes maybe, but for daily tasks no. Still, I am very eager to buy it and keep it.

 

@GoodSir you could use ThrottleStop or Intel XTU to undervolt the system; restrict frequencies only if undervolting isn't enough. Or just get a cheaper i5 CPU - something in $20 range.

 

Ok, thank you.
This might sound as a stupid question, but mind you, I am no expert. Will the lower voltages, and all other such modifications, put a strain on the system in the long run?

 

@GoodSir if it's stable, the system will work better in the long run; if it's unstable, you won't be able to use it. There are no cons to (reasonable) undervolting, only pros.

 

Ok, understood.
After you mentioned that an i5 should be about 20$, I searched some local online classifieds and found one. I wasn't aware that it sells for much less than what the shop was asking. After that, I have decided to narrow down my choice to the i5-2450m, but from a private seller, and that quad-core i7 for 50$. I fail to grasp the idea that I should pay 50$ for the dual core i7, since it just looks like a faster i5.

My guess is that the i5 should do the job without any problems whatsoever.