I get all my firewood for free ... well I have been, this past few years have seen a huge rise in demand and my source may dry up.
I would stay away from anything fast growing, it has much less heating value, for the same work, I call them weeds. I think you'll find that 8 acres will give you a lot of firewood, I never cut down a tree, my firewood is all windfalls / storm damage. I would look around and see what timber does well in your area, and stick to that.
I've reached the big '50' this year and all I plant is Ash, Oak, Beech + some wild/ bird cherry, rowan for the wild life ... I'm not thinking about what I can get out of it, I'm doing ok from someone elses planting, so I'm passing it on, and trying to improve on the types of trees for future wood gathers.
I've oak thats in 22 - 25 years and could be cut, but it would really be a waste, so I leave it for others ... I'm guessing you are in the 50+ bracket aswell, so I would be expecting that your wood cutting days are becoming shorter, as mine are ... but there's always a demand for quality timber, and some nice hardwood thinnings may bring in a nice sum as you approach retirement.
When I find my wee place I'll certainly plant some fruit trees ... a very useful crop, and they become an obsession ... check out stephen hayes on utube for a great guy about apples.
If you find you're running short of firewood you could possibly buy a lorry load of oak etc from the local woods, so helping the local community and saving your own stocks while growing something really worth while.
AIMHO
I've seen too many folks planting willow etc and finding that it needs a special harvester, needs to be chipped etc etc not the same as burning a nicely seasoned log in your wood stove.
I get carried away on these topics, sorry.
Cheers