I'd buy some classic jbls. They are easy to sell, to drive and will give you a lot of bang for the buck. Other upgrades will show well. You can always sell them quickly, at least in my opinion. I bought some 4343's for a wedding and sold them the following week for the same price. Just don't pay too much for them. Usually some old freak has had the cones redone and is selling them at a loss.
Good luck
Good luck