Want to upgrade laptop and install eGPU for under ~$250. Advice needed

[bilingual]

NOTE: I am aware of Thunderbolt solutions but my laptop doesn't support it so yeah!

I have a fairly recent laptop without dedicated graphics (Dell Vostro 2520 - HM75 chipset, i3-3110M 2.40 GHz with HD Graphics 4000, 4 GB RAM, 500 GB HDD, etc.) and I want to upgrade it so that I can play modern games on it with an eGPU providing the graphics horsepower.

For the eGPU, I wish to use a mini-PCIe to PCIe adapter (found one for ~$50 here - http://www.banggood.com/EXP-GDC-Laptop-External-PCI-E-Graphics-Card-p-934367.html, please see if there's a cheaper and/or better alternative), which should work on my laptop as I think it has a spare one from the user's manual. [Please confirm - Manual can be found here - http://downloads.dell.com/Manuals/all-products/esuprt_laptop/esuprt_vostro_notebook/vostro-2520_Owner%27s%20Manual_en-us.pdf]. I don't want to use my laptop's 65W charger to run the eGPU instead of a power supply, so the graphics card's power consumption should lie under it. As far as I know, one of the laptop's variant supports a GTX 620M, and since mine doesn't have it, I would have a mini PCIe 2.0 1x slot empty in my laptop's motherboard.

Overall, I need an elegant solution for gaming while using my laptop without the eGPU at ease. If everything goes right, all I need to do to switch to and from 'gaming mode' is to detach the laptop's keyboard and attach the mini-PCIe cable from the eGPU. [Again, the manual I shared above gives instructions on how to do it. Please see sections 'How to remove the keyboard' and 'How to remove the wireless card' for the procedure].

Since the eGPU would require a separate monitor to run modern games, I would prefer to have 30+ FPS at 1080p at high settings, and preferably 60 FPS for most of the games with fair amount of details. If there is a way to just use my laptop screen with the eGPU, then I should be able to get ultra settings in all games at native resolution (1366x768) for all games and maybe even do some upscaling to 1080 if possible.

The overall cost of the upgrade should be less than $250 or ~200-225€. I'll be buying parts from France, so please note that the overall cost should also consist of all taxes (TVA).

Sorry but I cannot provide a PCPP list as they don't have stuff for laptops, but here's what I have in mind for the parts:

GPU: Currently, a GTX 750 or 750 Ti seems to be the best option for me. Here are links for both on Amazon:

750: http://www.amazon.fr/MSI-N750-1GD5-graphique-GeForce-PCI-Express/dp/B00L5HDKAO/ [since it is only 106€ and have low power consumption, it looks like a good deal]

750 Ti: There are two options to choose from -

http://www.amazon.fr/Gigabyte-N750OC-2GL-graphique-GeForce-Express/dp/B00NJG6LXM/ [A great upgrade from 750 but the website does not clearly state the power consumption of the card]

http://www.amazon.fr/MSI-N750-2GD5-OCV1-graphique-PCI-Express/dp/B00JXLXSF6/ [The most expensive of the three but consumes only 55W according to the website while giving me 2 GB of dedicated memory.]

For the graphics, please tell me if 750 Ti is a worthy upgrade over 750, considering the rest of the system I have. If you have other suggestions, do note that I should be able to power it from my 65W DC adapter with a small buffer of power left just in case.

CPU: I found a used i7-3612QM processor currently on bid at Ebay (http://www.ebay.com/itm/Intel-Core-i7-Mobile-i7-3612QM-2-1Ghz-6Mb-SR0MQ-/181729666352), which is the best processor I can install on my laptop with similar TDP (35W) of my current processor. I'd love to buy it if it costs less than $50.

Since the CPU normally sells for a lot more than the bid at the time of writing ($150+ v/s $25 atm), is it worth the upgrade? Do note that with the i7 CPU, I would get 4 cores instead of 2 and some games (like Far Cry 4) need at least 4 cores and I'd like to play it.

BONUS: If I am able to get the solution for cheap and if RAM is a bottleneck, is it worth upgrading it to 8 GB for the cost?

It is a dream project I'd like to do soon. Please help me realize it!

 

[Calculagator]

This idea shows up pretty frequently here. It's good in theory but not in practice.

You laptop has a single mini-PCI-e adapter for the wifi card. It is most likely limited to only support wifi. There is no second slot. Laptop graphics do not use mini pcie-slots.

In the off chance that you could use your wifi slot to power a gpu, you will get poor performance since the slot is probably limited to PCI-e 2.0 x2 at best.

For the cost of the GPU, mini pcie adapter, external power supply, and monitor, you could buy a laptop with an actual GPU or even a dedicated gaming desktop. Both would give better performance and not carry the headache and risk of disassembling your computer every time you want to play a game.

Your laptop cooling system won't be able to handle the cpu you are looking at if it runs at all. It is cheap because the seller is in Russia.

 

[k1114]

You will need an external psu for any gpu. 65w is just enough for the components you already have. In the manual the vostro 2420 with the 620m comes with a 90w which also has a different mobo. Internal gpus on laptops don't use pcie slots. The majority are soldered and you can see in the vostro 2420 manual. The cable that connects the keyboard is delicate and will break rather soon if you plan to keep switching. It was never made to really be messed with much. I'm guessing along with an external monitor, you'd also have an external kb and mouse.

Changing out the cpu is also an issue. Even with the same tdp, that i7 will create more heat than your i3. Also having the same socket does not mean it will be compatible with your mobo bios. This is a bit tricky since they don't publish cpu support lists and contacting support may not get it either. Other than googling if others have done it, this is usually done at your own risk.