I am wanting to use non-stock cooling and I have heard good things about the Tuniq 120 http://www.newegg.com/Product/Prod [...] 835154001. However its dimensions are as follows:

Physical Spec
Fan Dimensions 120 x 120 x 25mm
Heatsink Dimensions 131 x 108 x 153mm

I have been racking my brain over what case I should get that would accomodate non-stock cooling and reading newegg reviews isn't cutting it.

I am currently looking at the pricey (would like a cheaper case) COOLER MASTER Stacker 830 and it has a width dimension of 9.8 inches. http://www.newegg.com/Product/Prod [...] 6811119103

But I have to keep in mind that the side case panel houses 4 120mm fans that will probably get in the way. Maybe I can remove 2 of those side fans and it will make room for the Turiq or a Thermalite 120 http://www.newegg.com/Product/Prod [...] 6835109140

I also have been looking at the Antec P180's http://www.newegg.com/Product/Prod [...] 6811129025 yet their width dimension is 8.1 inches.

First and foremost I am making a gaming machine with a budget of 1800-2000.00 dollars which will include the following.

Intel Core 2 Duo E6750 -- that I want to OC using a non-stock HSFAN coupled with a good case with alot of air flow that is quiet. I want to get it to 3.2 atleast or 3.4 and higher would be prime.

GIGABYTE GA-P35-DS3R -- heard that the P35 is really good when it comes to OC

Crucial Ballistix 2GB DDR2 800 (PC2 6400)

Western Digital Raptor 74GB 10,000 RPM Serial ATA150 - OEM
Seagate Barracuda 7200.10 320GB 7200 RPM SATA 3.0Gb/s Hard Drive - OEM

OCZ GameXStream 600W PSU

EVGA 8800GTS 320MB

AC5

ZALMAN ZM-MFC1 Fan Controller
http://www.newegg.com/Product/Prod [...] 6813999251

Windows XP

Samsung 226BW 22" Monitor

And choice of cooling.

Sorry for the long post, but I am trying to do as much research on proper cooling/case combo before purchasing.
If you are using non-stock cooling that are LARGE what cases and mobo's are you using?

Don't have an answer for your main question, but just to give you a little more headache; make sure the Tuniq fits your motherboard as well. Some of the newer northbridge heat spreaders are fairly large, and the capacitors can get in the way as well.
Btw, I'm also planning to OC the E6750 to 3.2GHz, but I'm going to try stock cooling first. These chips run pretty cool, so I would hold off on the Tuniq until you know you'll need it.
Also, take a look at the Antec 900 as well (just a personal note).

I don't think you have to worry. I just checked, and my scythe ninja http://www.newegg.com/Product/Prod [...] 6835185038 which is 150mm tall fits nicely on my Antec solo http://www.newegg.com/Product/Prod [...] 6811129018 case with 20mm to spare. The P180 should be the same width. I think that only cases with side fans will cause you a potential problem. Get the case you want first, then the cooler. If the cooler does not fit, then exchange it, Newegg is very good that way.