Adding a HD to 15.6" Javelin Laptop

Just found DS from NVIDIA website because I have been looking for a new laptop to replace my HP from '09. Haven't found a laptop till I came here that has everything I wanted. Have this planned out:
Chassis Model: Digital Storm Javelin 15.6 Inch Laptop (Model: S:7358)
Display: 15.6 Inch (16:9) (Resolution: 1920 x 1080) (Anti-glare) LED-Backlit Display
Processor: !SPECIAL PRICE: Intel Core i7 4810MQ (Up to 3.80Ghz) (Quad Core) (6MB Cache) (LIMITED TIME ONLY)
Thermal Compound: Stock CPU and GPU Thermal Compound
Memory: 16GB DDR3 1600MHz
mSATA SSD: - No Thanks
Storage Drive 1: 1x SSD (240GB Intel 730 Series)
Storage Drive 2: - No Thanks
Optical Drive: Blu-Ray Player (Blu-Ray 6x) & DVD/CD Writer
Wireless Card: Intel Dual Band Wireless-AC 7260 + Bluetooth 4.0
Graphics Card(s): NVIDIA GeForce GTX 860M 2GB with NVIDIA Battery Boost + NVIDIA Optimus
Windows OS: Microsoft Windows 7 Home Premium (64-Bit Edition)

My question is, later on, I can open a part on the back and add in my own HD into the system with the SSD already there? I like to know what all goes into my computers and make sure I have a good drive I can trust, all the other parts are parts I know for brands that are good.  For my hard drive, I want to make sure its one that would do well by putting in a Seagate and since none of the regular HDs listed have a name with them, I was thinking I can always add in my own once I got the system. From the pics, it looks like I could but want to check before I buy. Thanks ahead of time.