Need 14-16" tall case

I think you will have a problem.
Normally dual graphics cards require a full ATX motherboard which will be 12" tall, and they are normally mounted vertically with a psu on top or bottom.
With a standard psu that is 3.5" tall, there is little room left.
1. How great is your need for dual cards? Will a strong card like a GTX680, or even a Titan or GTX690 not suffice?
If one card will do it, there are a number of M-ATX cases like the Silverstone TJ-08E that is 14.5" tall.
2. Some M-ATX Z77 based motherboards have dual graphics slots that can support sli/cf.
The main problem is that two double slot cards will be installed next to each other. That means that the top card runs hotter.

If I read the specs correctly, your motherboard is M-ATX and supports only a single graphics card.
It also looks like the case cooling will be poor for a strong graphics card, let alone two.
In a desk, you will want good front to back airflow since a top exit will be restrictive.
I can recommend the Silverstone TJ-08E which has a 180mm intake fan that provides plenty of airflow.
http://www.newegg.com/Product/Product.aspx?Item=N82E16811163182
This asus P8Z77-M Pro will support dual cards:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131833
But, in general, I do not recommend dual cards when using a single monitor.
Here is my canned rant on that:
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Dual graphics cards vs. a good single card.

a) How good do you really need to be?
A single GTX650/ti or 7770 can give you good performance at 1920 x 1200 in most games.

A single GTX660 or 7850 will give you excellent performance at 1920 x 1200 in most games.
Even 2560 x 1600 will be good with lowered detail.
A single gtx690 or Titan is about as good as it gets.

Only if you are looking at triple monitor gaming, then sli/cf will be needed.
Even that is now changing with triple monitor support on top end cards.

b) The costs for a single card are lower.
You require a less expensive motherboard; no need for sli/cf or multiple pci-e slots.
Even a ITX motherboard will do.

Your psu costs are less.
A GTX660 needs a 430w psu, even a GTX680 only needs a 550w psu.
When you add another card to the mix, plan on adding 150-200w to your psu requirements.

Even the strongest GTX690 only needs 620w.

Case cooling becomes more of an issue with dual cards.
That means a more expensive case with more and stronger fans.
You will also look at more noise.

c) Dual cards do not always render their half of the display in sync, causing microstuttering. It is an annoying effect.
The benefit of higher benchmark fps can be offset, particularly with lower tier cards.
Read this: http://www.tomshardware.com/reviews/radeon-geforce-stutter-crossfire,2995.html

d) dual card support is dependent on the driver. Not all games can benefit from dual cards.

e) cf/sli up front reduces your option to get another card for an upgrade. Not that I suggest you plan for that.
It will often be the case that replacing your current card with a newer gen card will offer a better upgrade path.
The GTX780 and amd 8000 series are not that far off.
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