Do you play in pool rooms often? If so what brand table do they have? I believe in practicing on what you play on.
Diamonds play great, we all know that. They have deep shelf pockets so they pocket differently than a Gold Crown. You can't make a GC play like a Diamond even if you put Diamond rails on,
Have fun with it, good luck.
I beg to differ with that comment. My GCI plays a lot like a Diamond after having the rails modified, pockets tightened, and cushions replaced. I have tested and compared it with a 9' Blue Label repeatedly, if there is something different in how they play I or others have not noticed, although those modifications come with a price tag. Next I want to go play on an unmodified Gold Crown again to see how big the difference is.
As far as the OP's question if you see having this table for years to come I think your best choice is to buy that Diamond. Its a commercial table, you should be able to get at least 50 years out of it and if you care for it well I dont see a situation where you lose money on it. Home tables just do not compare to commercial tables. I doubt if you did modify your current table that it would increase its value at all so you would kind of be beating a dead horse so to say by investing more in it.
As far as owning a 9' table and shooting league and tournaments on a 7' table the bar box will seem like a toy when you play on it. I am in the same situation, have a 9' and shoot on 7's, the only thing you have to get used to is the speed difference, that should come quick. Playing on a small table while owning and playing often on a big table should also give you added confidence.