On The GWE website, there's an article on hps/Mh suggestions for different sized tents. No suggestions for a tent your size, but we can use the general square foot ratios to guess. They suggest 600-1000 watts for a 4x4, 16 square feet You're dealing with a 6.5x6.5 tent, 42.5 Sq ft, so you'd want 2.65 times as much light. 1600-2650 watts, so two 600s would be pretty underpowered. Two 1000s would fulfill the wattage requirements, but wouldn't really fit your room. Having a large square like that means only having two bulbs would mean the have to cover a rectangular space, which isn't a great way to have an even spread. I would actually suggest getting 4 hoods and use them to split your room into smaller, more manageable squares. 4 400 watt ones would meet the requirements, and 4 600 watt ones would give you pretty much full saturation. If you're unable to afford 4 hoods right now, getting two to start will still allow you a good deal of effective growing space, just not the whole tent. You could buy two 1000 Watters to get the most out of those two hoods now, and then downscale them to 600 each when you're able to get more. Make sure to get dimmable ballasts so you can reuse them with lower wattage bulbs.
Here's a solid grower talking about how he sets up his room, which may be useful to you since he runs 4 hoods in a large space.
https://m.youtube.com/watch?v=JmtM9f9Ns90
About your yields question, many people are able to pull a pound from 16 square feet, so if you're able to complete your grow without a hitch, you could pull quite a bit more than that. A fully saturated and healthy tent could definitely pull in 2-3 pounds with skill. It's great that you're looking to learn, and one thing I would suggest doing is try to keep reading gwe articles until there are no more related ones you haven't read yet, then do it again if you feel fuzzy on some topics still. There is a lot about growing that is following directions, bit it's not always as clear as putting x amount of nutrients in a reservoir and making sure lights are a certain distance. If your plants show signs of stress, then there usually is a simple solution, but you have to know what you're looking at to know what it is. Of course, if you're unable to tell what the problem is, that's what this site is for! There are a bunch of people here who could also look at what's wrong and perhaps know the answer. Growing cannabis can definitely be an art, but you don't need to be an artist to grow some serious dankness.
lastly, your plant count. The answer can vary depending on how much you decide to do in the way of training, but a reasonable range would be anywhere from 12-24 for your whole space. Here's an article nebula made showcasing an auto grow she did in a 2x4 with 3 plants and she pulled 6.7 oz!
http://www.growweedeasy.com/auto-flo...urnal-250w-hps
If you got through this wall of text, congrats! The articles on gwe are more interesting than me so you'll do fine ha. And remember, the important thing isn't to never make mistakes, it's to be active enough to be able to see those mistakes, learn from them, and adjust accordingly.
happy growing
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