What To Spend

You can spend an eye watering amount on a long HDMI cable. The most expensive I've seen was a 10m lead for sale at £250. I'm sure it would not take much searching to eclipse that figure. My advice would be to  try a mid priced cable and see how you get on, as mentioned in a previous post; you can always add a booster if you are having problems. Bandridge have a good priced 10m cable which can be purchased for around £70.

The image below shows the Bandridge BVL1210.

This is a version 1.4 High Speed With Ethernet BVL1210 cable found. This lead is fully 3D compatible. It has braided shielding, hard gold plated plugs and is made with 100% copper. These leads actually have a certificate style hologram on the packaging to confirm 3d capability at a given length.
Bandridge are a European company based in Holland. They launched in 1990 and have a great reputation for providing quality cable solutions. They also own  the high end Profigold brand which is distributed world wide.