Advice on over clocking, heat sync and CPU/Mobo/ H100i

Yes, it will work. The radiator can only fit on the top.

You should be able to OC the 4770k even with a regular air cooler. Your motherboard without the plastic armor is pretty much the same as a high end P8Z87-V (most likely the deluxe based on the lack of DVI) which is a decent motherboard for overclocking. It uses low heat solid capacitors and high quality mosfets with heat sinks on them. The thermal armor and aux fans are designed to enhance the cooling of these parts which can help with overclocking as well. There are better Asus motherboards out that are designed for even more extreme OC'ing such as the Maximus VI series. Some of those boards come with built in water blocks for the mosfets instead of the passive heatsinks on the The Sabertooth. If you plan on a modest OC like 4.0 - 4.5 GHz, then there is no need for the Maximus VI. In my opinion, the Sabertooth boards are meant more for air cooling than liquid cooling, but the H100i should work just fine on it.

I personally have the predecessors to both the Sabertooth Z87 and 4770k, the Sabertooth Z77 and 3770k. I have been overclocking it since the day I built it at 4.5 GHz (1.0 GHz over stock) using a Hyper 212 Evo. I actually removed the two small aux fans that go in the armor because they were the loudest things in my system. The temps did not change at all. In a 21 - 22c room, the internal CPU core temp sensors never go past 35c at idle and never pass 70c under load. If I run a bench test or Prime 95 it will go up to 75 - 80c.

My suggestion is to use a better thermal paste such as Arctic Silver. The 4770k is supposed to run a bit hotter than the 3770k and 2700k. Both the 3770k and 4770k have a different heat spreader design than the 2700k and all previous CPUs all the way back to the LGA 775 socket. The 4770k uses thermal paste inside in between the heat spreader and the core itself. Before, this was soldered on. Some people believe that this is why the newer CPUs run hotter and can't overclock as well. A few have actually gone as far as taking a knife to the heat spreader and removing it and replacing the thermal paste with Arctic Silver. They did get better temps proving the theory. But this is not recommended and will void the CPU's 3 year warranty.

Also, make sure you have a high quality power supply. There are reports of the Haswell CPU not being compatible with older PSUs or low quality ones since at idle their amperage draw falls to .005a compared to the Ivy Bridge's .05a. This could cause the PC to shut off. Look for "Haswell compatible" or something similar. But, any Sandy Bridge compatible or up PSU that is also 80-plus rated should be fine.

Yes, the stock paste is okay but it doesn't last as long. It tends to harden after a few years which turns it into an insulator instead of a heat conductor. It is worth the extra $10 especially if you are going to OC. The higher temps will hasten the hardening of the stock Corsair paste. The stock paste comes already pre-applied on the H100i water block. Just take a soft paper towel, put some rubbing alcohol on it and wipe it off. Then take a clean towel w/ rubbing alcohol and get the rest until the copper is a mirror like shine. Once you have the H100i mounting bolts in place and the CPU in the socket, put the Arctic Silver on the CPU itself. Use just a pea size dab in the center. Then install the heat sink and tighten it down. Some people like to spread it on the CPU, but tests have shown that the pea size dab in the center gets the better temps. Actually, the same tests found that an "X" formed over the whole CPU gets the best temps, but not by much.

See the test results: http://www.pugetsystems.com/labs/articles/Thermal-Paste-Application-Techniques-170/

AS 4 or 5 should be fine. They are about the same.

Yes, I just got the UVH upgrade pack II for 360 on BL2. I'm also planning on getting it for PC but haven't leveled up any characters past 61 yet. I'll look you up on Steam.