Maximum PC

Hello all,

I am building a new computer, with this motherboard
ASRock Z77 extreme4
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157293
This board came with some free memory.
http://www.newegg.com/Product/Product.aspx?Item=N82E16820220685
The free memory has the following specs
2x4GB
DDR3 1600 (PC3 12800)
Timing 9-9-9-24
Cas Latency 9
Voltage 1.5V

I purchased 2x8GB of memory with the following specs (I didn't even notice my board had free memory, oh well)
http://www.newegg.com/Product/Product.aspx?Item=N82E16820233280
DDR3 1600 (PC3 12800)
Timing 10-10-10-27
Cas Latency 10
Voltage 1.5V

My question is this, Am I better off just running the 16 gigs of corsair vengance by themselves, or adding the extra 2x4gb viper in addition?
I want to have at least 16gb ram, but if it will still run well with 24, Ill take it. But if adding the 2x4gb modules will make my rig slower Ill just sell it on ebay I mostly need to know because I don't want to try to reinstall ram after installing the Noctura NH-D14 (that cooler is huge)

The rest of the build is a FT02 case, msi 660ti video card, 250gb samsung sd, Noctura NH-D14, and the Intel i5 3570k processor with a Corsair 650 gold modular power supply. I tossed in a cheap dvd burner and a 2tb samsung drive as well. Should be a fun build

Thanks for any opinions.

Just EBay the 2x4GB. It might work just fine but you won't notice any performance increase. On the other hand it could cause your computer to crash, so IMO just EBay em.

Thats what I was thinking, but good to get second opinion
Thanks for your help.