Need advice updating Lenovo T420

So I almost caved and bought a new laptop for myself but I decided I's stick with my T420 and try to get it up to speed. Anyway, I recently just put a 256GB SSD (crucial M4 sata3) in it and added 4GB of RAM (8gb total now). I also updated the wifi adapter to an Intel Centrino Advanced-N 6205 Dual Band Mini PCI-e. I'm pretty satisfied with everything, especially the SSD. I'm definitely in the hunt to use this computer to it's highest capability while not spending too much money to upgrade, which so far I have accomplished that. But I still have some questions.

First off, I read some forums and the Advanced-N 6205 is the only "better" wifi adapter I could find, that I knew would work upon startup without messing with the BIOS stuff (which I literally know nothing about).
I feel like it's a decent adapter compared to the realtek that it came with, but I also feel like there might be something better that I don't know about. Do any of y'all have any suggestions on buying a better wifi adapter for so I can have the best speed possible?

Also, I'm curious about the mPCI-e slot in the back of it as well. I've googled some stuff on it but it was general info about the slot so I figured I'd ask y'all for more creative uses. I know you can use this for extra storage such as a small SSD drive, but I also noticed the antennas. How can I maximize that slot and this machine in general? I'm not much of a gamer so I don't need any updates pertaining to that. I just like to utilize features/updates that most people don't mess with. For example I'd like be able to use a cableCARD from my cable company to watch TV, rather than paying for a cable box fee every month ( the miniPCI-e slot wouldnt work for that would it?) I noticed the advanced docking station has a PCI-e situation going on but I don't know much about all of that. Any advice would be awesome with extending the life of this computer. I've never done any of this **** before so but I'm pretty intrigued by all these tweaks.

If y'all don't want to explain everything just tell me what to google and I'll look it up myself.

Thanks

Also, with all these updates and what not, I am curious how long will this notebook will realistically last as my primary, everyday computer.

 

@prm0008 sadly you can't put anything better without fighting whitelist. If you don't use TPM, however (e.g. for disk encryption) you can just flash the modified BIOS and simply turn it off after; the machine will work anyway, but will beep annoyingly every boot if you don't turn off TPM after flashing modified BIOS. Then, you can put 7260AC which is the optimal option for the money. But if your router doesn't support 802.11AC, it'll behave just like 6205.

The slot you're referring to is combo mSATA/WWAN slot. You can put any mSATA SSD inside, it's only whitelisted for WWAN i.e. mobile broadband - and that's what antennae are for. You can get whitelisted WWAN card for less than $10 e.g. the one inside Lenovo in my signature - but it won't support 4G LTE speeds. Alternatively, after removing whitelist you can put an LTE card of the corresponding form-factor, though they are usually many times more expensive.