Best Intel CPU Under $125

E6800. It's mentioned in the "Best Gaming CPU for the Money" TH series, November edition. link: http://www.tomshardware.com/review [...] 791-2.html

Since you're on LGA 775, there's not much choice when it comes to cheap upgrades. Most LGA 775 products under 125$ are the E5xxx series, and trust me, you don't want those. The E6800 is a 3.33 GHz part, pretty fast for gaming and other stuff.

The Hyper 212+ is a good bang-for-the-buck cooler. It's what's taking the heat off my i5-750 right now.

Lastly, go to ASUS's webpage and look at your motherboard's downloads page. Since the E6800 was surely released after your motherboard, you might have to update your BIOS to use the newer CPUs. Check your BIOS version (either by going in the BIOS itself or using a utility like CPU-z) and look at the CPU compatibility chart of your motherboard. Check which BIOS version supports it. If the BIOS version listed there is older or the same as your current BIOS version, then you don't have to upgrade. Otherwise, upgrade. Make sure you don't lose power while flashing your BIOS, otherwise you can end up with a nonfunctional motherboard.

There's not much difference between the 2. The E7500 has 3MB L2 cache versus the E6800's 2MB. The E6800 has a higher stock clock speed at 3.33GHz vs the E7500's 2.93GHz, although that could be equalized by an overclock. Either of them would be a great choice for a dual-core LGA775 processor.

The Hyper 212+ is a tall cooler indeed. I have a HAF 922 case, so the height isn't an issue, but if your case is thin, then yes, you might want to get a shorter cooler.

Quite far, I would think. Using water-cooling on something like the E6800 is like using a flamethrower to light a match (OK, maybe not). You can probably reach ~3.8GHz on that thing. As long as temps don't reach high 70s you should be good. When I have my i5 overclocked to 3.4GHz, I peak at 70 with prime95 (Room temp is high, around 28-30), so I think you can push that thing even further.