This all seems silly to me Chris... Not because you aren't thinking about it, but because you are asking for a answer to a question which hasn't actually been asked.
That is, what is it that is desired? WHY was speaker cable purchased? What is the cat-6 for? What is the intent, what is the goal? If you don't have a goal, then how can we recommend a plan to achieve that goal?
Building a house is awesome! It's a very unique time to really wire the heck out of the home. If you actually have the access, and the right to run wires, then just go nutso-crazy about it.
So, let's talk, and be serious about the talk.
1. Where are the TVs going in the house? Remember that if there are any 'old' tube TVs, they are relics. So, all new TVs for the next 50+ years that the house is there will want a flat panel display (or what comes next). So, pick TV locations right now, think about the layout of rooms, where the TVs will go, and then wire appropriately.
2. Every TV must be fed from the sources which are needed. The easiest and most common location is by placing a TV on a stand and having sources located right under it, but if there is a goal to wall-mount a TV, then that TV needs power on the wall, and a way to get cables to that location. If the path is straight up and down, then it's easy to put wires behind the wall at any point if there is no firestop in the way. But, across studs should have at least 1.25" flexible conduit (Carlon) put in place. This gives a path for wiring from the equipment to the TV at any time.
3. Speakers and distributed audio, etc. should be extremely carefully thought out and planned. I like having the option of audio anywhere, and Monoprice makes decent enough speakers for $50 a pair or so. Regardless of actually putting speakers in, go ahead and run the wiring. Consider that all wiring should be run to a central location which has plenty of room for equipment. Always better to have it next to the telephone, cable, and network distribution center.
4. Networking! I'm sure you have NEVER had issues with Wi-Fi not working. I'm sure your friend has never had an issue as well, so as I'm sure this is the case, then there's no need to put in a wired network. Wait... What's that you say? You HAVE had issues over the years with wireless connectivity? Well, what do you think they are putting into $100 Blu-ray players? Top shelf Wi-Fi products? Of course not! You are also talking about streaming video (most likely) and Internet content. So, you MUST put in a good wired network and it should be in place to all 'critical' locations. Those location (IMO) include: One in a good 'desk' location in each bedroom. One to a home office, or perhaps on each wall of an office. And one to any equipment locations for 'Smart' devices. We also put one behind our couch in the family room in case a laptop in use doesn't play well with Wi-Fi. The goal of Wi-Fi use for general web-surfing is fine, but heavy use in a home can eat up wireless bandwidth, and more importantly Wi-Fi from A/V gear can really suck balls. Get the wires in place. Cat cabling is incredibly inexpensive and completely worth it. I have no issues with Monoprice cabling that I've used.
5. Consider the rest... Anything and everything. Think about what you may dream of having in the house. If it's a stand alone house, then consider outdoor locations as well. Speakers in the garage, on the porch, out front. All the 'weird' locations. I have over 20 zones of audio in my setup and can hardly imagine setting up a home with less than 8 zones. It's pretty easy to think them up if you look around. Consider TV locations over fireplaces if that is to happen. Consider fireplaces themselves and if they should be setup in a FAR more A/V friendly manner.
There are dozens of things which can be done. But, after the drywall is up, the options become far less likely unless you will repair drywall.
I'm in the later category. Putting in recessed lights, adding lighting control, putting in all those speakers, TVs, control, etc. It's way easier to do it up front, and far less money if you come up with a list of what you want to accomplish so that recommendations can be made.
Remember! HDMI didn't exist 10 years ago. If you put an HDMI cable in a wall, and it's then drywalled into place, what's the game plan for when HDMI is replaced with something else? Plan for it, install for it, be ready for it.
