Upgrading MONITOR for gaming

I'm currently sporting a 60hz TV, and I was thinking about upgrading to a monitor in the near future. But I have some doubts.
1) Is there a noticeable difference between a tv and a monitor, I only know of input lag...is that really noticeable in games like counter strike?
2) I dont know if I should go 120 or 60 hz. I plan on getting a 390 in the near future, but in any case, I would be playing most of my games at 60fps, with some exceptions like csgo, which I would play at 120 (I heard it's night/day difference). Can playing at 60fps on a 120hz refresh rate give me some problems? I feel like 1440 wouldnt be much of an improvement so I'm not really considering it.
3) I'm under the impression that IPS monitors are the best, am I wrong?
4) As long as I stay with Asus, Benq, LG, Samsung I should be ok, right?. other good brands?
Also I was thinking that I may need several hdmi ports but I realized I can just get a hdmi hub, it will be a bit unaesthetic on my desk but it's practic.

With a TV you pay more for the additional ports and the built in tuner, they won't be binned/built specifically for PC and gaming use, but usually are fine. Considering though that you want this for gaming then yes a monitor will be better for the job compared to a TV. Maybe the difference won't be instantly noticeable or even noticeable at all depending you how you see things, unfortunately there is no way we can tell you as it is personal, you would have to see and judge the difference personally.

If you can find 120hz with all the other features you want too then yes. Higher refresh rate will look better, but for me it is not worth sacficing image quality for refresh rate, I will expand on this in a second. You can play 60fps stuff on a 120hz panel of course and there will be no down side to this. Just like plating a game at 30fps on a 60hz panel does not make a difference other than you can see it is not at full speed, basically there are zero compatibility issues if you are worrying about that.

IPS has the best colour gamut (range) and therefore image quality, more colour more fine detail. VA is the next step down from IPS and TN a further step down from VA. I said I would expand on the refresh rate thing, IPS tends to have the lowest refresh rate, it is just the way the panels function. Va is the middle ground in both color/picture reproduction and refresh rate, and TN has the worst reproduction but the highest refresh rates. So as above if you can find an IPS with all the features/options you like and 120hz, get that budget permitting. Because IPS has lower refreshrates you pay a premium for high refresh rate IPS.

Go with what you feel comfortable with, but realistically there are only a few companies making panels for monitors so every brand will only be using panels from a handful of companies like Samsung, Sharp, LG and a few others regardless of the rand on the monitor. If you find one from a company you are unsure of post it up and people can tell you if it is good or not.

Hopefully that answers your questions, if not shout and I will clarify.

thanks! you were really thorough. The more I sit on in the more I fear that 1080 might become obsolete faster than I think. It's something that I discussed other times, my mind tells me that 1080 to 1440 is too little a leap in res for the average consumer to endorse and make it a standard, but there's something in the back of my head that is doubtful...or maybe it's just me always wanting the shinier and more detailed thing :/
On the other hand the 390 (the card I'm planning to buy) barely does 1440@60 at the moment, so in the next years it may struggle, with more detailed games coming out.
yeah I guess I'm gonna go with a 1080@120 ips monitor, the next upgrade is going to be to 4K, when 4k gaming is feasible

The 390 actually does better then normal at 1440, of most games it will max out and still give 60 pretty stably. Look around for benches of it. The 290 I Have is great at 1440 or very close to it at about a half million pixels out because I run at 2048x1536. It should run fantastic. Whoever told you barely 60 at 1440 was either a green team fanboy or had their facts wrong. at 2160p (4k) it will struggle all right to keep it at 60 but 1440 should be no worry to it.

I watched the Jayz2cents comparison video between the 390 and the 970. Maybe I was exagerrating with "barely": it did 40 with the witcher3, 59 on metroLL, 63 gta5, 51 farcry4, 37 crysis3. I'm torn

Those are some of the hardest current games to run. So yeah those number seem about right. There is always VSR so you can use a 1080p monitor and bump the res up in the Catalyst Control Centre.

You could even do that when you get eh card and before you get the monitor and test the performance yourself to see if it is worth it, it wont be a misrepresentation of performance either as the card will be working as if pushing 1440p is what you monitor is at. So you could get a feel for it and if it work to your liking then get that monitor resolution.

also I'm looking right now and 1440p monitors seem to be way more expensive than 1080 here in EU, is that the case in the us as well?

No idea, I am in the EU too so yeah I can understand the prices you are seeing. There is always Dreamsellers ebay and Korean 1440p and 2160p monitors that have been reviewed many times on TekSyndicates youtube channel.