:-)
Ready to drop 50k?
Didn't think so.
First:
http://www.kjartan.org/swordfaq/section15.html
Be less concerned with the quality of the blade and more with the balance and size.
My preference is for a katana that reaches from the ground up to slightly below my diaphragm. You should get out a tape measure and find the right length blade for you. This should trim down your options. Once you know the length you simply have to find one that is well balanced.
There is no point in dumping cash into a sword that you will never fight with. After you have trained with the bamboo sword for a while you will have an idea of what you are looking for. Picking a "balanced" sword is a purely personal decision. Training will make up for what is lacking in the balance of the weapon itself. To find out if a katana is balanced... use it. Try out some forms and see how it feels. Try a few and get a basis for comparison and you will begin to understand the differenes between them and how it effects your control and power. Then you should be able to plink down 500 or so for it.
You won't get a quality folded bladed for 500 that you can stake your life on, but for training it is more then adequate.