GTX 980
reference PCB (PG401, GM204-400-A1)
reference cooler (silver/black NVTTM-based, black backplate)
reference specs
NVidia OEM GTX 980 (discontinued)
ASUS GTX980-4GD5
ELSA GD980-4GERX - Japan
EVGA GTX 980 04G-P4-1980-KR (discontinued?), EVGA GTX 980 04G-P4-2980-KR (new electrical components, new VBIOS, less coil whine)
Gainward GTX 980 - Europe/Asia
Galax GTX 980 NVTTM - Europe/USA
Gigabyte GV-N980D5-4GD-B
Inno3D N980-1DDN-M5DN - China
Leadtek WinFast GTX 980 - China
Palit GTX 980 - UK
PNY GTX 980
MSI GTX-980-4GD5
Zotac ZT90201-10P (standard "GTX 980" logo)

reference PCB
other cooler and/or other specs -
EVGA GTX 980 04G-P4-2981-KR (ACX2.0)
Galax GTX 980 Black (glassy black stylized NVTTM, 11.06" long) - Europe/USA
MSI GTX-980-4GD5-V1 (angular black stylized NVTTM)
Point of View VGA-980-A1-4096 (AXC2.0 variant, I think) - Europe
Zotac ZT90205-10P ("Zotac" logo, sleeker NVTTM, 1139/1240MHz clock)

and one last manufacturer exists -
Colorful iGame (not listed above because they only make non-reference designs) - China

I got this one and installed in in my G20 works great 🙂

http://www.newegg.ca/Product/Product.aspx?Item=N82E16814133563&_ga=1.11049524.1431727736.1424797764

A lot of users report good overclocks with those PNY GTX 980 cards .

For me is very stupid to pay around 550-600$ for reference clock when 20$ more is 120-130MHz higher clock.
Even on same reference card with same cooler. Why you need constantly to check AB or Precision and clock...
Example reference clock is 1126MHz, 20$ more is 1241MHz, that's 1000 Graphics Points more, but that's not all,
you can use BIOS from other card with same PCB only other cooler ACX 2.0 with 1266MHz or even BIOS from same reference PCB only Hybrid AIO Cooler 1291MHz...if your chip can resist.
At the end that's 1291-1126MHz=165... Your default clock is +165 GPU Offset, but card is still same...reference.
But result in 3DMarks completely something else than reference and only what you need to do is to set fan profile, not clock.
You can change memory clock with BIOS Tweaker for 100-150MHz if you want...just for little OC.

The primary advantage of lower-cost reference cards is their potential bang-for-the-buck overclocking gains ("efficiency", some people would say).

A vendor like PNY makes only one (reference) GTX 980 card, no other GTX 980 cards. Many people speculate that your odds of winning the silicon lottery with a card like this from a manufacturer like this are increased because the manufacturer hasn't already culled out the best/fastest GPU ASICs (and GDDR5) to use in their higher-tiered (and more costly) products. They use every single GPU part they can get in the same product, and even if these are already binned by TSMC/NVidia, chances are that a number of better ones slipped through.

A second advantage with these reference cards is the NVTTM cooler. It was basically designed for a 250W card but is mounted on a 165W card. This provides a lot of spare overclocking headroom, even if the chips happen to be lemons. Non-reference "improved" air coolers are, ugly truth be told, sometimes inferior and often roughly equivalent to the (server-based) mighty NVTTM, only a few are actually superior - many card makers use their own custom coolers to market their brand identity and cut production costs.

My two EVGA-overclocked 1391MHz GTX 980 cards were CDN$875 each (after including backplates), and I am hardly able to run their clocks any higher than about 1450MHz - while I see a fair number of people clocking their "stupid" $625 reference cards at 1.5GHz and beyond. A price difference which could almost buy a third reference card in itself - and I strongly suspect 3-SLI at plain reference speeds (ignoring overclocks entirely) will still surpass 2-SLI at 15%-over-reference speeds in any real-world or benchmark metric.

@Korth, Thanks for the wealth of information buddy! I think Ill go with the PNY 980 GTX model because Best Buy appears to have them in stock again and they are priced at 549.99, basically a 50-70 dollar savings. I likely wont be overclocking anytime soon because the G20AJ case is so slim im still worried about overheating issues even if the fans exhaust out the back of the unit. I almost wish there was a third party 'base' for this unit with an additional fan to run along the bottom to keep pushing air up (imagine how some of the Xbox 360 external fans worked)

The reference NVTTM cooler expels almost all of the card's heat outside the chassis, through the air cutouts. Probably the best choice for your crowdy small form factor chassis.

"Improved" coolers typically blast air all over the card to cool the card itself at all costs - some is exhausted out of the chassis, some is blown off the edges of the card into the rest of the chassis, where it can recirculate and doesn't help to cool anything else on the motherboard. Gigabyte's hard-to-find-small-print specifically states that you should install a rear-exhaust fan above the GPU to exhaust heat, and that you should install ducted airflow or other cooling upgrades if you intend to run multiple GPU cards - they even bravely admit that their mighty trademarked patented WindForce fans and cooler are only designed to cool a single GPU card in a single GPU system - I think a lot more manufacturers should indicate this as well.

Is there an admin that can sticky important threads like this?