Which soundcards would you reccomend?

My uncle uses something similar like this and he also records guitar

I have an Sound Blaster Z, its a really good sound card for 70-80 euros.

You could get something like the M-Audio Audiophile 192 but it's PCI rather than PCIe, and it's a bit more expensive than you mentioned.

There's also regular consumer sound cards that can be good at doing recording too, but it'll take some research to find which ones are the best for what you want.

How exactly are you connecting an acoustic guitar to line input?

I use a Sound Blaster Z, has a very good sound for all stuff you're doing like gaming, movies, music and even for audio producing. Remember that you need equivalent Headphones and/or speaker benefit from this, you should also check possibilities to connect instruments to it like your uncle. I have no comparison to other soundcards besides the former model of the soundblaster Z but I really like it I use Sennheiser HD598 Headphones and the difference to a onboard soundcard is huge, you can connect it to PCI or PCIe. So if that is your budget I can recommend the soundblaster if you want to going on really high quality audio editing/hearing you should look for a more expensive one. Hope this helps.

What do you think of this entry-level sound card?
http://www.newegg.com/Product/Product.aspx?Item=N82E16829132013
Or I can even go with this one?
http://www.newegg.com/Product/Product.aspx?Item=N82E16829132020

I use a Focusrite Scarlett 2i2. It's an external USB soundcard with 2 hybrid inputs (XLR and 6,3mm Jacks merged) and it does the job very well. Just plug your guitar in directly with a jack cable or mic the amp and you can record. Not even that expansive.
http://us.focusrite.com/usb-audio-interfaces/scarlett-2i2

Edit:
For guitar recording you could also take a look at this forum:
http://www.ultimate-guitar.com/forum/showthread.php?t=1541771

Internal soundcard is more than good for everything, dedicated sound cards are a waste of money (for anything other than offloading the small bit of processing off of the cpu). If you want to learn something, watch this, they provide great information on why dedicated soundcard is a waste.
If you want to record a guitar, look into DI (direct input) boxes / recording interface for guitars, like from m-audio, line6 or other reputable brand. I myself am using the Line6 Studio GX, which is probably the most basic you can go when it comes to DI boxes, it records with absolutely no latency and no noise, but there are other, better/more expensive options as well.